Awesome

12 months books

The Well-Grounded Rubyist (2nd edition) by David A. Black (Amazon)
Programming Ruby (2nd edition): The Pragmatic Programmers' Guide by Dave Thomas, with Chad Fowler and Andy Hunt (O'Reilly)
Agile Web Development with Rails 5 by Sam Ruby (PragProg)
The RSpec Book: Behaviour-Driven Development with RSpec, Cucumber, and Friends by David Chelimsky, Dave Astels, Zach Dennis, Aslak Hellesøy, Bryan Helmkamp, Dan North (PragProg)
Practical Object-Oriented Design in Ruby by Sandi Metz (site)
99 Bottles of OOP by Sandi Metz (site)
Design Patterns in Ruby (site)
The Passionate Programmer: Creating a Remarkable Career in Software Development by Chad Fowler (PragProg)
EXCEPTIONAL RUBY by Avdi Grimm (site)
Confident Ruby by Avdi Grimm (site)
The Clean Coder: A Code of Conduct for Professional Programmers (Amazon)
Metaprogramming Ruby 2: Program Like the Ruby Pros by Paolo Perrotta (PragProg) + Ruby Metaprogramming Screencast by Dave Thomas (PragProg)
Refactoring: Improving the Design of Existing Code (Amazon)
Everyday Rails Testing with RSpec (Leanpub)
Minitest Cookbook by Chris Kottom (site)
Working with Ruby Threads - (PragProg)

Ruby under microscope by Pat Shaughnessy (site)
Rails as she spoke by Giles Bowkett (site)
Ruby Hacking Guide (site)
Head First Ruby (site)
Rails AntiPatterns by Chad Pytel (site)
Growing Rails Applications in Practice (PragProg)
Crafting Rails 4 Applications (Amazon)
Working with ruby threads (PragProg)
Ruby performance optimization (PragProg)
Ruby Science: The reference for writing fantastic Rails applications (link)
RubyFu - Ruby for hackers (gitbook)
Kestrels, Quirky Birds, and Hopeless Egocentricity - Raganwald's collected adventures in Combinatory Logic and Ruby Meta-Programming (Leanpub)
Refactoring. Ruby Edition (Professional Ruby Series) (site)
Eloquent Ruby (Professional Ruby Series) (site)

Seven Languages in Seven Weeks (PragProg) - A Pragmatic Guide to Learning Programming Languages
Pragmatic Programmer: From Journeyman to Master (PragProg)
Introduction to Algorithms, Third Edition (Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, Clifford Stein) (site)

Awesome Software Craftsmanship (github) - "As aspiring Software Craftsmen we are raising the bar of professional software development by practicing it and helping others learn the craft"