On the heels of its first F8 Developer Conference in three years, Facebook open-sourced this extensible animation engine for iOS and OS X. On top of basic animations, Pop supports spring and decay dynamic animations with an API, allowing quick integration with existing Objective-C codebases, thereby enabling the animation of any property on any object.
Developed by Jordan Scales, this simple isometric graphics library for HTML5 canvases allows for easy creation of isometric graphics. Isomer is divided into three basic components: points, paths and shapes. It also has 2D paths, 3D modeling to scale, the ability to translate and rotate shapes, and smaller classes to reduce code repetition.
#5: GitHub Cheat Sheet has been a long-time occupant of this list.