Awesome

GBDK Playground

It has 16 kB of RAM, man.

Samples

Blank	Hello World	Small Sprite
Minimum required code	Print Hello World!	Render small 8x8 sprite

Big Sprite	Big Sprite Animation	Input State
Render big 16x16 sprite	Animate big 16x16 sprite	Read joypad state

Input Wait	Move Sprite	Background
Wait for button input	Move a sprite using joypad	Render a full-screen background

Window	Beep	Simple SHMUP
Renders a window	Make a sound	Very simple SHMUP

Huge Sprite	Drawing	Detect GB Type
Renders a huge 40x64 sprite	Built-in drawing functions	Detect which GB is being used

Save RAM	Font	Link
Save/load variables	Load a new font	Send/Receive data using link cable

Color	More coming soon...
Use palettes for Game Boy Color	Contributions are welcome!