Awesome

Awesome Opensource Unity

to make the Unity game-dev life happier and future proof, here is a full list of assets and packages.

👉🏼 Please submit a PR for any obsolete, updated or new entry! You can do it just editing this README and GitHub will do everything. Let's keep this list awesome!.

Games
Open Source Packages
- 2D
- 2D Bones
- AI
- AI Tools
- AR
- Animation
- Asset Bundle
- Camera
- Character Controllers 2D
- Character Controllers 3D
- Controller Mappings
- Console
- Database
- DOTS
- EdTech and Game Based Learning
- Editor
- Effect and Shaders
- Environment
- Framework
- Framework - visual
- Gameplay
- Input
- Level Editor
- Light
- Localization
- Lua
- Materials
- Math
- Meshes
- Monetization
- Networking
- Physic
- Plugins
- Procedural Generation Systems
- Pooling System
- Profobuf
- Scriptable Object
- Scriptings
- Services
- Sounds
- Timeline
- Tweening
- Vehicle
- UI
- Utilities
- Video
- Voxel
- VR
Assets
- 2D assets
- Icons
- Collections
- Creation Tools
- Audio
Articles
Books

Games

Adventure

San Andreas Unity - An open source reimplementation of GTA San Andreas game engine in Unity.

Educational and Social Impact

Antura and the Letters - the award winning open source literacy and language learning game for kids.
Idiomatic - Aan educational game developed to teaching English to native Portuguese speakers.
La Noria - an open source videogame about social innovation in Malaga.

Cards

Card-Game-Simulator - Create, Share, and Play
Pokemon Unity - A LEGACY Unity project to help build Pokémon-esque RPG games.

Puzzle

Nodulus - A puzzle game with a clever twist. Based on the mathematical theory behind plank puzzles, consists of a grid of cubes and rods which can be rotated with a swipe.
Angry Birds style game - An effort to replicate a level and relevant mechanisms of Rovio's famous Angry Birds game, built in Unity game engine. Source code is provided for educational purposes.
Match-3 game - A match-3 game in Unity (like Candy Crush and Bejeweled).

RPG

Darkest Dungeon - Darkest Dungeon port in Unity. Almost completely identical to the original.
Hogwarts - A Hogwarts (Harry Potter) open sandbox game made in Unity.

Runner

InfiniteRunner3D - Creating an infinite 3D runner game in Unity.

Sandbox

CubeWorld - Minecraft like game made in Unity.

Shooter

Multiplayer-FPS - A multiplayer first-person shooter game based on Unity3D. Different types of input devices are supported, including Kinect, Xbox controllers, Leap motion, and VR Glasses.

Strategy

Starcraft Unity3D - A recreation of the classic Starcraft game by Blizzard, on Unity3D.

Open Source Packages

2D

Unity2D-Components - A constantly evolving array of Unity C# components for 2D games, including classes for pixel art cameras, events & messaging, saving & loading game data, collision handlers, object pools, and more.
StaticBluredScreen - Non-realtime (=static) screen blur for Unity. Easy to use background for dialogs.
AtlasImage - AtlasImage is a graphic component use SpriteAtlas for uGUI. In addition, add useful sprite selector and border editor to the inspector.
SpriteDicing - Extension for Unity game engine to work with diced sprites.
DataRenderer2D - Make mesh like line, polygon, etc in unity3d.
UnitySpline2D - 2D spline utility for Unity.

2D Bones

DragonBonesCSharp - DragonBones C# Runtime.
Spine Runtimes - Collection of Spine runtimes including with Unity3d version.

AI

ML Agents - Unity Machine Learning Agents Toolkit .
GOAP - A multi-threaded GOAP (Goal Oriented Action Planning) system for Unity.
Unity Movement AI - A library of common movement AI scripts known as Steering Behaviors. You can use these scripts to help your NPCs move around your game.
Crystal AI - A Utility AI for C# and Unity.
EpPathFinding.cs - A jump point search algorithm for grid based games in C#.
EpPathFinding3D.cs - A 3D jump point search algorithm for cube based games in C#.
goap - Goal Oriented Action Planning AI in Unity.
UnitySteer - Steering, obstacle avoidance and path following behaviors for the Unity Game Engine.
A Star Pathfinding for Unity - A Star Pathfinder, 3 axis, multithreaded for Unity.
openpath - Open source pathfinding for Unity.
unity-path-finding - Shortest path finding with Dijkstra's algorithm for Unity.
NPBehave - Event Driven Behavior Trees for Unity 3D.
fluid-behavior-tree - A pure code behavior tree micro-framework built for Unity3D projects. Granting developers the power to dictate their GUI presentation.
Unity3d-Finite-State-Machine - Very good and easy FSM An intuitive Unity3d finite state machine (FSM). Designed with an emphasis on usability, without sacrificing utility.
Path-Creator - Path creation asset for Unity game development.
NavMeshPlus - Unity NavMesh 2D Pathfinding.
NavMeshSurface2DBaker - NavMeshSurface2DBaker is a Unity Package that provides functionality to bake 2D colliders into NavMeshSurface components.
Brainiac - Behaviour tree editor for Unity3D.
behaviac - Behaviac is a framework of the game AI development, and it also can be used as a rapid game prototype design tool. behaviac supports the behavior tree, finite state machine and hierarchical task network(BT, FSM, HTN).
DotRecast - A port of Recast & Detour, navigation mesh toolset for games, Unity3D, servers, C#.

AI Tools

AI Game DevTools (AI-GDT)
StableDiffusionUnityTools - Editor assets generation via Stable Diffusion.

AR

AR Foundation Essentials - AR Foundation examples created with AR Foundation.
XRTK - The Official Mixed Reality Framework for Unity.

Animation

unity-animator-helpers - A micro-framework for changing Unity 3D's Animator parameters with ScriptableObject(s). Designed to make going from custom scripts to Animator parameters easy. Works with 2D or 3D projects.

Asset Bundle

AssetBundleManager - An asset bundle manager for Unity.

Camera

Unity Pixel Camera - A resolution independent pixel perfect camera for Unity.
DeadSimple Pixel-Perfect Camera - An exceedingly easy-to-use pixel perfect orthographic camera script for 2D scenes in Unity. Punch in a few specs and you've got a working pixel perfect camera. It's that easy.
Dynamic Multi Target Camera for Unity - Concise Unity library which dynamically keeps a set of objects (e.g. players and important objects) in view.
FulldomeCameraForUnity - Fulldome Camera for Unity 2019.

Character Controllers 2D

CharacterController2D - Similar to the built-in Unity CharacterController component. It has a similar API (mainly a move method that takes a delta movement) and provides a firm base with which to make a super solid controller using Unity's 2D system.
Unity 2D Platformer Controller - A customizable 2D platformer motor that handles mechanics such as double jumps, wall jumps, and corner grabs. Includes a player controlled prefab that can be dropped into any scene for immediate support.
Ultimate-2D-Controller - A great starting point for your 2D controller. Making use of all the hidden tricks like coyote, buffered actions, speedy apex, anti grav apex, etc

Character Controllers 3D

Kinematic Character Controller - Robust Character Controller for Unity
NaughtyCharacter - Third Person Controller for Unity.
Advanced Rigidbody FirstPerson Controller - Rigidbody Based FirstPerson Controller.

Controller Mappings

Console

Unity3d-BeastConsole - Console for all your unity needs.
consolation - In-game debug console for Unity.
Lunar Unity Mobile Console - High-performance Unity iOS/Android logger built with native platform UI.
Unity In Game Debug Console - Easy to use in-game debug + command line interface. Also on the asset store.

Database

SQLite4Unity3d - SQLite made easy for Unity3d.

DOTS

unity-ecs-navmesh - A demo implementation of Unity Entity Component System with NavMesh.
ECS-Tween - Simple Unity tweening system using ECS that works with GameObjects!.
PlasticTween - Tween Library for Unity3D(ECS+JOBS).
unity-jtween - A job-based tween library for Unity.
KNN - Fast K-Nearest Neighbour Library for Unity DOTS.
SpriteSheetRenderer - A powerful Unity ECS system to render massive numbers of animated sprites.
NativeCollections - Native Collection Types for Unity https://jacksondunstan.com/articles/tag/native-collection.
Hydrogen.Entities - A collection of helpers for work with Unity's ECS framework, used in our games.
Unity-2D-Pathfinding-Grid-ECS-Job - ECS Burst Job System 2D Pathfinding.
EntitySelection - A minimal solution for selecting entities in the unity sceneview.
Easy-Road-3D-ECS-Traffic - Unity DOTS/ECS traffic using Easy Roads 3D for the data.
IcSkillSystem - A simple and reusable skill system.
EntitiesBT - Behavior Tree for Unity ECS (DOTS) framework.

EdTech and Game Based Learning

RAGE ecosystem
uAdventure - Serious game editor for Unity based on eAdventure.
Unity Tracker - Unity gleaner tracker that uses csharp-tracker / RAGE.

Editor

Alchemy - Provides a rich set of editor and serialization extensions for Unity.
Unity-QuickSheet - Unity-QuickSheet enables you to use spreadsheet file data within Unity editor.
Unity3D Rainbow Folders - This asset allows you to set custom icons for any folder in unity project browser.
Reorderable List Editor Field for Unity - Reorderable List Editor Field for Unity.
Reorderable Inspector - Automatic reorderable lists for Unity game engine components.
Vexe Framework (VFW) - An editor extension that offers much more advance editor extensibility features than what comes out of the box with Unity.
Tidy Up - Neat little tool! to help you keep your Unity projects organised by throwing assets in their designated folders.
Unity Psd Importer - Advanced PSD importer for Unity3D.
property-drawer-collection
unity-symlink-utility - A small extension that adds a menu item to add folders as symlinks in Unity.
UnityDefineManager - Easily manage global defines in Unity.
Texture3DPreview-for-Unity - This package enables interactive previews of Texture3D assets in Unity's Inspector window.
unity-colourlovers-importer - Unity editor tool to load colours and palettes directly from COLOURlovers.com.
shortcuter - Shortcut utility for Unity.
unity-editor-spotlight - MacOS-like Spotlight file search in Unity.
Unity-Reorderable-List - Extended version of the Reorderable List in Unity.
UnityEditorJunkie - Editor scripts to make working with the Unity Editor better.
UniOmni - Global search for Unity.
Readme - Readme component for Unity, attachable to any GameObject to document what you can't in a script or the file system.
Unity-AssetDependencyGraph - An Asset Dependency Graph for Unity.
MyBox - MyBox is a set of attributes, tools and extensions for Unity .
Unity-Finder - Find Asset in Unity.
Unity-Editor-Toolbox - Tools, custom attributes, drawers and extensions for Unity Editor.
enhancer - A collection of utilities to enhance the Unity Editor.

Effect and Shaders

Unity 5 Effects - Effect storage space for Unity 5.
Outline-Effect - Outline Image Effect for Unity.
unity-frosted-glass - Frosted glass material made in unity.
unity-delaunay - A Delaunay/Voronoi library for Unity, and a simple destruction effect.
Helicopter effect
SSMS - Screen space multiple scattering for Unity.
KinoGlitch - Video glitch effects for Unity.
Temporal - Temporal Reprojection Anti-Aliasing for Unity 5.0+.
SMAA - A highly customizable implementation of Subpixel Morphological Antialiasing for Unity.
Typogenic - Signed-distance field text rendering for Unity.
AtmosphericScattering - Atmospheric Scattering for Unity.
Facepunch.Highlight - Mesh outline effect.
crest-oceanrender - An advanced ocean system implemented in Unity3D.
HologramShader - Hologram Shader and Material Editor for Unity.
ShaderlabVS - ShaderlabVS is a Visual Studio plugin for Unity Shaderlab programming.
Kamakura Shaders - Kamakura Shaders is a collection of shaders and components focusing on Non-Photorealistic Rendering for Unity with a bunch of features and adjustable parameters in a user-friendly interface.
ShaderProject - A container for all sorts of handy shaders.
ShaderForge - Shader visual scripting.
Ocean_Community_Next_Gen - Next gen iteration of the unity community ocean shader.
ToonShading - A collection of "Toon" shaders for Unity based on a stepped PBR approximation.
AnisotropicStandardShader - A modified version of Unity's Standard Shader using an Anisotropic GGX BRDF.
SpriteGlow - A sprite glow effect for Unity game engine.
Mirror (Script) - A mirror script.
HoloShield - Highly customizable sci-fi shield / force field shader for Unity3D. Allows you to set edge power & color, inner texture scrolling, waviness, scale pulsation and procedural intensity noise. Implements tessellation for low-poly base meshes.
VerticalDissolve - Procedural vertical dissolve shader. Highly customizable. Tweak edge color, noisiness & waviness, rim light, emission scrolling and more.
SphereDissolve - Customizable procedural spherical dissolve shader for Unity3D, for all your customizable procedural spherical dissolve needs!.
TexturePanner - This repository hosts a shader for Unity3D whose main goal is to facilitate the creation of neon-like signs, conveyor belts and basically whatever based on scrolling textures.
RadialProgressBar - Customizable radial progress bar shader for Unity3D. Allows you to set arc range, minimum and maximum colors, textures, radius, and a few more things. Create HP Bars, Speedometers, rank progress, etc!.
Unity-ShaderSketches - Sketches made with ShaderLab in Unity.
Arktoon-Shaders - Alternative Unity shaders made by synqark.
Unity-Shaders - Shader demo - More than 300 examples.
UltimateOutline - The easiest way to achieve outlines in unity.
Outlined-Diffuse-Shader-Fixed - This is a fixed version of diffused outline shader from http://wiki.unity3d.com/index.php/Outlined_Diffuse_3.
BNAO - A tiny, GPU-based Bent Normal and Ambient Occlusion baker for Unity.
ezy-slice - An open source mesh slicer framework for Unity3D Game Engine. Written in C#.
UnityPCSS - Nvidia's PCSS soft shadow algorithm implemented in Unity.
Ceto - Ceto: Ocean system for Unity.

Environment

roadbuilder - Easy-to-build realistic roads in Unity. Foundation of any simcity game.
hedera - Paint 3D ivy in the Unity Editor, watch procedurally generated meshes simulate growth and clinging in real-time.
Photosynthesizer - Unity plugin to procedurally sprout foliage throughout your scene.

Framework

Zenject - Dependency Injection Framework for Unity3D.
Entitas-CSharp - Entitas is a super fast Entity Component System (ECS) Framework specifically made for C# and Unity.
adic - Lightweight dependency injection container for Unity.
uFrame.Complete - All in one repo, includes: Kernel, Designer, Architect, MVVM, ECS.
QFramework - Your first K.I.S.S Unity 3D Framework.
ecsrx.unity - A simple framework for unity using the ECS paradigm but with unirx for fully reactive systems.
GameFramework - A free framework for Unity that will help drastically increase the development speed and feature set of your games.
gocs - GameObject Component System for Unity.

Framework - visual

xNode - Lets you view and edit node graphs inside Unity.
Fungus - Awesome and powerful Adventures and Visual novel engine.
BlueGraph - Like xNode, but on UIElements.
Node_Editor_Framework - Node Editor framework for Unity3D.

Gameplay

UnityArcRayCast - Arc raycast utility using projectile formulas.
UnityGameplayAbilitySystem - A unified framework for implementing ability systems in Unity.
Inventory-Pro - The best-selling Inventory System for Unity - now free and open-source!.
Quest-System-Pro - The powerful Quest and Conversation Tree System for Unity - now free and open-source!.
lospro - The Lightweigt Line-of-Sight & Hearing System for Unity - now free and open-source!.
Inventory - A Diablo 2-style inventory system for Unity3D.
RPGCore - RPGCore is a toolkit for producing RPG games and mechanics for Unity.
NoteEditor - Note editor for rhythm games.

Input

Lean Touch - Powerful and complete touch library. paid additional examples available.
InputManager - Custom InputManager for Unity.
InControl - An input manager for Unity that tames the cross-platform controller beast.
InputBinder - Easily bind input events to methods in Unity.
TouchKit - Gestures and input handling made sane for Unity.
TouchScript (Recommend) - Complete multitouch solution for Unity: Win8, TUIO, Mobile.

Level Editor

Tiled2Unity - Export Tiled Map Editor (TMX) files into Unity.
UnityTile3D - Simple 3D Tile Editor.
2DTileMapLevelEditor - 2D Tile Map Level Editor for Unity.
HexTiles - Unity Hex Tile Editor.
giles - GILES: A Runtime Level Editor for Unity3D.
floorplan - A Sims-Like Unity Level Design Plugin.
realtime-CSG-for-unity - Realtime-CSG, CSG level editor for Unity .
RoadArchitect - Road Architect for Unity.
PrefabPainter - A basic prefab painter for the Unity3D game engine.
Terrain-Stamps - Stamps for the Unity Terrain Stamp Tool.
StampToolExtended - Extended version of the Unity Terrain Stamp Tool.
YAPP - Yet Another Prefab Painter - Tool for conveniently and flexibly adding huge amounts of prefabs to your Unity scene.

Light

Aura - Volumetric Lighting for Unity.
Simple Light Probe Placer - A simple tool for Unity3d and it help you easily place Light Probes in your scene.
VolumetricLights - Volumetric Lights for Unity.
Rimlight - Customizable rimlight shader for Unity that includes pulsation and noise scrolling. Give your scenes that extra oomph!.

Localization

Lean Localization - Quickly add multi-language support. text, sounds, load CSV.
Localization System - Localization System for Unity can be used for both RTL and LTR languages (based on CSV file), Images, Audios, LayoutGroups and RectTransforms with detailed Documentation.

Lua

slua (Recommend) - Fastest lua binding via static code generating for Unity3D and mono.
xLua (Recommend) - xLua is a hot-fix solution plugin for Unity3D, it supports android, ios, windows, macOS, etc.
UniLua - A pure C# implementation of Lua 5.2 focus on compatibility with Unity3D.
MoonSharp - An interpreter for the Lua language, written entirely in C# for the .NET, Mono, Xamarin and Unity3D platforms, including handy remote debugger facilities.
LuaProfiler-For-Unity - LuaProfiler-For-Unity.

Materials

Public Domain Textures - Tons of 8K PBR Materials under CC0 License.

Math

MathUtilities - A collection of some of the neat math and physics tricks that I've collected over the last few years.

Meshes

UnityMeshSimplifier - Mesh simplification for Unity.
MeshDecimator - A mesh decimation library for .NET and Unity.
SplineMesh - A Unity plugin to create curved content in real-time with bézier curves.
roadcreator - A free road creation tool for unity.

Monetization

unity3d-levelup - Unity3D F2P game progression library - worlds, levels, missions, scores, records and more. Part of The SOOMLA Framework - for game design, economy modeling and faster development.
unity3d-store - Unity in-app purchase & virtual economy library. Part of The SOOMLA Framework - for game design, economy modeling and faster development.
Google Mobile Ads Unity Plugin - Official Unity Plugin for the Google Mobile Ads SDK.

Networking

FishNet - Fish-Networking: Unity Networking Evolved is an easy to use, high performant, feature-rich Unity based networking solution. FishNet is free while offering features previously only seen in paid options. .
UnitySocketIO - A socket.io client for unity3d.
websocket-sharp - A C# implementation of the WebSocket protocol client and server.
Hazel-Networking - A low level networking library for C# providing connection orientated, message based communication via TCP, UDP and RUDP.
MassiveNet - Unity3d UDP networking library focused on high-CCU, multi-server architecture.
Nakama - An open-source distributed social and realtime server for games and apps by Heroic Labs. It includes a large set of services for users, data storage, and realtime client/server communication; as well as specialized APIs like realtime multiplayer, groups/guilds, and chat.
Barebones Master Server - Master Server framework for Unity.
Forge Networking Remastered - In short, Forge Networking is a free and open source multiplayer game (multi-user) networking system that has a very good integration with the Unity game engine. You wanna make a multiplayer game or real time multi-user application? This is the library for you.
Facepunch.Steamworks - Another fucking c# Steamworks implementation.
MagicOnion - gRPC based HTTP/2 RPC Streaming Framework for .NET, .NET Core and Unity.
Mirror - a high level Networking API for Unity, supporting different low level.
Transports
lidgren-network-gen3 - Lidgren.Network is a networking library for .NET framework, which uses a single UDP socket to deliver a simple API for connecting a client to a server, reading and sending messages.
LiteNetLib - Lite reliable UDP library for Mono and .NET.
LiteNetLibManager - Higher level implementation for LiteNetLib.
UNet-Controller - A CharacterController based controller for Unity's new Networking system.
Steamworks.NET - Steamworks wrapper for Unity / C#.
UnityHTTP - A TcpClient-based HTTP library for Unity.
SocketIoClientDotNet - Socket.IO Client Library for .Net.
MLAPI - A game networking framework built for the Unity Engine to abstract game networking concepts.
Networker - A simple to use TCP and UDP networking library for .NET. Compatible with Unity.
SmartFoxServer 2X - A comprehensive SDK for rapidly developing multiplayer games and applications with Adobe Flash/Flex/Air, Unity, HTML5, iOS, Windows Phone 8, Android, Java, Windows 8, C++ and more.
Colyseus - Multiplayer Game Server for Node.js. Demo with Unity3D.
UnityWebSocket - Web Socket client for Unity.
RESTClient - REST Client for Unity with JSON and XML parsing. (Features JSON helper to handle nested arrays and deserializing abstract types).
SpeedDate - SpeedDate Masterserver: Connecting Players.
UnityLockstep - Deterministic Lockstep with serverside framerate for Unity.
ET - Unity3D Client And C# Server Framework.
unity-fastpacedmultiplayer - Features a Networking Framework to be used on top of Unity Networking, in order to implement an Authoritative Server with Lag Compensation, Client-Side Prediction/Server Reconciliation and Entity Interpolation.
Entitas-Sync-Framework - Networking framework for Entitas ECS. Targeted at turnbased games or other slow-paced genres.

Physic

BulletSharpUnity3d - A fork of the BulletSharp project to make the Bullet Physics Engine usable from C# code in Unity3d.
Graphics-Raycast - GPU-based raycaster for Unity.

Plugins

Reign Unity Plugin - This Reign API is a cross-platform, unified API for the Unity game engine.
unity-webview - A plugin for Unity 5 that overlays WebView components on Unity view. It works on Android, iOS, Unity Web Player, and macOS (Windows is not supported for now).
google-analytics-plugin-for-unity - Google Analytics plugin for the Unity game creation system.
unity-native-sharing - A Unity plugin to open native sharing dialogs on iOS and Android, primarily for sharing screenshots.
Unity3D Android notification plugin - Unity3D Plugin for Android local notifications with example project.

Procedural Generation Systems

DungeonGenerator - A dungeon generator for Unity.
Procedural-Cave-Generator - Unity scripts that procedurally generate ready-to-use cave meshes.
unity-procedural-tree - Procedural tree builder for Unity.
unity-procedural-flower - Procedural flower generator for Unity.
ProceduralToolkit - Procedural generation library for Unity.
wavefunctioncollapse - Walk through an infinite, procedurally generated city.
ProceduralLevelGenerator-Unity - Unity plugin from procedural dungeon generation.

Pooling System

Unity-QuickPool - Simple pooling toolkit for Unity game engine.
RecyclerKit - Object pool manager for Unity.
ObjectPool - Instead of creating and destroying new objects all the time, this script reduces garbage by pooling instances, allowing you to seemingly create hundreds of new objects while only actually using a recycled few.
unity-object-pool - An elegant object pool and manager implementation for Unity.

Profobuf

protobuf-net - Protocol Buffers library for idiomatic .NET.
protobuf-unity - Automatic .proto files compilation in Unity project to C# as you edit them.

Scriptable Object

unity-atoms - Tiny modular pieces utilizing the power of Scriptable Objects.
Scriptable-Framework - A Unity Framework for modular app creation based on ScriptableObject architecture, data oriented design and event driven programming to help programmers and designers adhere to the 5 SOLID programming principals.
yaSingleton - A singleton pattern implementation for Unity3d. Based on ScriptableObjects instead of the conventional MonoBehaviour approach.
SOFlow - A ScriptableObject oriented design SDK.
ScriptableObject-Architecture - Makes using Scriptable Objects as a fundamental part of your architecture in Unity super easy.

Scriptings

UnityNativeScripting - Unity Scripting in C++.
unity-python - Python plugin for Unity3D.
YarnSpinner - Yarn Spinner is a tool for building interactive dialogue in games! .
UniScript - Brings C# scripting into Unity which acts as native code.
SlowSharp - C# interpreter written in C#.

Services

Google Play Games plugin for Unity - Google Play Games plugin for Unity.
line-sdk-unity - Provides a modern way of implementing LINE APIs in Unity games, for iOS and Android.

Sounds

usfxr - A C# library used to generate and play game-like procedural audio effects inside Unity. With usfxr, one can easily design and synthesize original sound in real time for actions such as item pickups, jumps, lasers, hits, explosions, and more, without ever leaving the Unity editor.
Unity-Beat-Detection - Musical beat detection and audio spectrum analysis for use with the Unity game engine.
LibNoise.Unity - Coherent noise library for Unity, a port of LibNoise.
Reaktion - Audio reactive animation toolkit for Unity.
MusicEngine - Make music synced game with Unity / ADX2 / Wwise.

Timeline

SpineTimeline - Animate SkeletonAnimation or SkeletonGraphic with Unity's Timeline.

Tweening

DOTween (Recommend) - A Unity C# animation engine. HOTween v2.
LeanTween - LeanTween is an efficient animation engine for Unity.
GoKit - Lightweight tween library for Unity.
Unity Tweens - Lightweight tween library for Unity.
Uween - Lightweight tween library for Unity.
ZestKit - Tween library for Unity. The best of GoKit and GoKitLite combined in an easy to use API.

Vehicle

Tork - Vehicle system for Unity.

UI

FairyGUI-unity - A flexible UI framework for Unity.
MiniMap - Unity3D mini map (radar) system (Asset Store link - https://www.assetstore.unity3d.com/en/#!/content/33729 ).
LoopScrollRect - UGUI ScrollRect reusing cells, to improve performance, loading time and draw calls.
MaterialUI - MaterialUI is a UI kit for Unity that follows Google's official material design guidelines.
Unity-UI-Extensions
EnhancedScrollView - Cool 3d scoll view for Unity(NGUI 3D UGUI support).
Beautiful Text Outline for Unity UI - Beautiful text outline for Unity UI.
uGUI-Effect-Tool - Vertex color UI Effect for Unity UI (uGUI).
Unity-UI-Polygon - Polygon renderer for the new Unity UI.
muip - Modern UI Pack for Unity engine.
lomenui - Stylish UI package for Unity engine.
ultimatehudskins - Stylish HUD layouts for Unity engine.
looader - Loading screen solution for Unity engine.
UIEffect - UIEffect is an effect component for uGUI element in Unity. Let's decorate your UI with effects!.
ParticleEffectForUGUI - This plugin provide a component to render particle effect for uGUI in Unity 2018.2+. The particle rendering is maskable and sortable, without Camera, RenderTexture or Canvas.
ShinyEffectForUGUI - Shiny effect of uGUI, which does not need mask or normal map.
FancyScrollView - A scrollview component that can be implemented flexible flexible animation.
Juicy Healthbar - A Juicy Health Bar from @reuno's Unite LA talk.
UIWidgets - UIWidget is a Unity Package which helps developers to create, debug and deploy efficient, cross-platform Apps.
PageTurningUIEffect - A page turning UI effect made with unity, the paper deformation is determined by the pins' position on it.
Unity-WinForms - Windows Forms wrapper for Unity.
Delight - Component-oriented UI framework for Unity https://delight-dev.github.io/.
CharTweener - Unity3D - DOTween extensions for tweening TextMeshPro characters.
UnityRecyclingListView - A fast scrolling list component for Unity UI which recycles its child elements.
sci-fi-ui - The uGUI Sci-Fi UI Design for Unity - now free and open-source!.
LiquidSwipeUnity - Butter smooth full page swiping animation with a masked wave effect in Unity.
Unity-UI-Rounded-Corners - This components and shaders allows you to add rounded corners to UI element.
RapidGUI - Unity OnGUI(IMGUI) extensions for Rapid prototyping/development.
ugui-mvvm - Unity3D uGUI mvvm databinding via the standard IXChanged interfaces used in wpf (INotifyPropertyChanged, INotifyCollectionChanged, etc).
Recyclable-Scroll-Rect - Recyclable Scroll Rect reuses or recycles the least number of cells required to fill the viewport. As a result a huge number of items can be shown in the list without any performance hit. .
UnityGUI - UGUI Panel Systems for navigation, animation and more.
UGUIExtend
Rewired.UI.Hotkeys - The plugin for Guavaman's Rewired Unity Asset that provides an easy-to-use API for showing controller hotkeys to the player at runtime based on their bindings and input method.
TMPEffects - Easily apply text animations and other effects with custom tags

Utilities

LINQ to GameObject - Traverse GameObject Hierarchy by LINQ.
Moments - A quick GIF replay recorder for Unity.
FrameCapture - A simple frame-by-frame capture tool for Unity to record perfectly smooth, supersampled replays or cinematics.
UniGif - GIF image decoder for Unity.
unityassets - Assorted assets previously on sale on the Unity Asset Store, now free on GitHub.
UnityToolbag - Variety of Unity scripts and tools.
C-Sharp-Promise - Promises library for C# for management of asynchronous operations.
3DMath - Unity C# 3D Math methods library.
Projeny - A project and package manager for Unity.
Unity Size Explorer - Visualize how much space each asset in your Unity game takes and quickly optimize your game's file size.
UnityStudio - Unity Studio is a tool for exploring, extracting and exporting assets from Unity games and apps.
InGameReplay - Allow you to record the transform of any objects to replay it.
UniRx - Reactive Extensions for Unity.
UnityMainThreadDispatcher - A simple, thread-safe way of executing actions (Such as UI manipulations) on the Unity Main Thread.
UnityPSDLayoutTool - A tool used to import a Photoshop Documents (.psd files) into the Unity Game Engine.
Rant - Robust text engine for procedural generation and postprocessing.
E7Unity - Common Unity resources.
mmd-for-unity - MikuMikuDance for Unity.
Unity.Library.eppz - Collection of libraries for Unity.
Alchemy-Circles-Generator - A simple procedural generator of alchemy circles.
odin-serializer - Fast, robust, powerful and extendible .NET serializer built for Unity.
UnityAsyncRoutines - An extremely lightweight Unity library for creating and managing asynchronous coroutines for easy, straight-forward multi-threading and parallellism.
fullserializer - A robust JSON serialization framework that just works with support for all major Unity export platforms.
IMP - Billboard imposter baking for Unity.
UDBase - Module-based game template for Unity. Modules in UDBase are called Controllers, their implementation can be replaced without changing your project source code.
graphy - Graphy is the ultimate, easy to use, feature packed stats monitor and debugger for your Unity project.
NuGetForUnity - A NuGet Package Manager for Unity.
GoogleSheetsUnity - Get data from your private Google Sheets to Unity! (Read-only).
unity-routines - Replacement for Unity coroutines that supports hierarchical routines and pooling.
CropTexture - Crop and resize texture in unity editor! Open it: Press F1.
demilib - A library of various utilities and tools for Unity.
SerializableCallback - UnityEvent and System.Func had a child.
bitstrap - BitStrap is BitCake's collection of Unity tools that improve our workflow.
NaughtyAttributes - Attribute Extensions for Unity.
Unity3DRuntimeTransformGizmo - A runtime transform gizmo similar to unitys editor so you can translate (move, rotate, scale) objects at runtime.
UnityPack - Python deserialization library for Unity3D Asset format.
UnityOctree - A dynamic, loose octree implementation for Unity written in C#.
CoroutineChain - Unity3d, Coroutine, scripting.
disruptor-unity3d - Basic implementation of Disruptor for Unity3d.
uREPL - In-game powerful REPL environment for Unity3D.
RuntimeUnityEditor - In-game inspector and debugging tools for applications made with Unity3D game engine.
Deform - A fully-featured deformer system for Unity.
OnionRingUnity - Auto 9 slice sprite generator.
UnityMultiBuild - Batch build for multiple platforms from within the Unity editor.
UnityCsvUtil - Lightweight but type safe CSV serialise/deserialise of objects.
InkPainter - Texture-Paint on Unity.
WaveformProvider - Provide a texture to simulate waves with Unity. Require InkPainter.
DataBind - Simple data binding for Unity.
GradientGenerator - A Unity script to generate multiple variants of evenly distributed Gradient based on input AnimationCurve.
Dialogue - Node based dialogue system.
Unity-EasingLibraryVisualisation - Front end visualisation of 40 common easing equations.
UnityGoogleDrive - Google Drive SDK for Unity game engine.
unity-mulligan-renamer - Mulligan Renamer tool for the Unity Editor allows for quick and safe renaming of many assets and gameobjects at once.
Xamarin.Forms.Unity - Xamarin.Forms for Unity (Platform implementation for Unity Game Engine).
WhatUsesThis - Right click an asset and get a list of assets that use it.
UnityTimer - Powerful and convenient library for running actions after a delay in Unity3D.
PixelSpriteGenerator-Unity - A port of the PixelSpriteGenerator to C# for use with the Unity3D game engine.
WeightedRandomSelector - Very fast C# class for weighted random picking.
SmartAssembler - Smartly Assembly your Project.
GetComponentAttribute - A simple DI plugin for getting MonoBehaviour components just with an attribute over fields.
unity-utils - Different help scripts for Unity engine.

Video

Vimeo Unity SDK - Easily stream your Vimeo videos into Unity or record and publish out to Vimeo.
VLC for Unity - LibVLC plugin for Unity to integrate multimedia playback inside your Unity apps and games.

Voxel

MagicaVoxel - Free to use Voxel editor (even for commercial).
UnityVoxelTools - Collection of Voxel Utilities for Unity.
VoxReader - A library to read .vox files created with MagicaVoxel.

VR

VRTK - A productive VR Toolkit for rapidly building VR solutions in Unity3d.
NewtonVR - A virtual reality interaction system for unity based on physics.
MixedRealityToolkit-Unity - MixedRealityToolkit-Unity uses code from the base MixedRealityToolkit repository and makes it easier to consume in Unity.
Google VR SDK for Unity - Google VR SDK for Unity http://developers.google.com/vr/unity/.
TButt - A lightweight multiplatform VR interface for Unity.
VRWorksAudio-Unity - Unofficial implementation of NVIDIA's VRWorks - Audio for Unity3D.
Lightweight-VR - An open sourced, light weight, VR input framework. This is basically an empty Unity project that's been setup for easy VR integration without having to pull down any packages. No need for Steam VR or OVR plugins.
VR Builder - A Unity plugin for creating interactive VR applications by using a visual editor instead of coding.

Assets

2D assets

Icons

I made 700+ RPG icons free for use for your game - 700+ RPG Icons(The filesonic URL ending with "Lorc_RPG_icons.zip" still works).
game-icons.net - 3443+ Game Icons licensed under CC BY 3.0.
EffectCore's VFX Packs - Paid AAA visual effects.

Collections

Unitylist - The best GitHub Unity repositories search engine.
Armedunity - Shooter focused forum.
itch.io
Game Assets
Game Dev Market
Unity Assetstore - Official asset store for unity.

Creation Tools

Aseprite - Animated sprite editor & pixel art tool.
AssetForge - Easily create simple assets in seconds (Paid).
BFXR - Make sound effects for computer games (Flash required).
Mixamo - Free to use animation mixing tool with free animations. Not allowed to use in open source projects.

Audio

Sonniss GDC 2018 Pack - Free to use 30GB worth of audio files.
unminus.com
dig.ccmixter.org
freesound.org
freesfx.co.uk
zapsplat.com
gamesounds.xyz
freemusicarchive.org

Articles

Books

Game Programming Patterns - Free and Paid available.