A small disclaimer, the code in the snippets is often not that well tested as the cocos code. Not every snippet is a complete solution, see them rather as a source of inspiration or starting point for your own implementation.

• Dynamic light source
• Simulate torchlight
• CCMutableTexture, get/set individual pixels using OpenGL
• Electricity
• CCUIViewWrapper, manipulating UIViews using Cocos2D
• Curved lines
• [box2D] fixed timestep implementation
• Scrolling backgrounds and parallax
• Tiled maps gaps/artifact/black lines fixes
• Tessalating, drawing masked sprites
• Crop/mask a sprite
• Camera zooming vs layer scaling
• Alternative camera implementation
• Joystick implementation
• Looping/scrolling menu
• Orbit camera, remove fisheye effect
• Gaussian blur
• Clip a screen region
• Tiled map optimizations
• Joystick class
• Collision detection with rotated CGRect
• Collision detection between partly transparent sprites
• Add a 3D model
• Optimize particle systems
• Tiled object layer support
• Spacemanager, objective-c wrapper for chipmunk
• "Scratch Off" render texture alpha effect
• Hiding resources in an app
• Encrypt data
• MVC for cocos2D (cocosMNC)
• Rope implementation
• Scale while center point stays at same position
• Pinchzoom, like fieldrunners
• Panning and zooming
• CCPhysics, simple collision detection
• Rendering a texture filled polygon
• Reflection
• UIGesture recognition support