Cocos2D is a tremendous opensource resource for the iPhone that is going from strength to strength http://www.cocos2d-iphone.org/about Features include Scene management (workflow) Transitions between scenes Sprites and Sprite Sheets Effects: Lens, Ripple, Waves, Liquid, Twirl, etc. Actions (behaviors): Trasformation Actions: Move, Rotate, Scale, Jump, etc. Composable actions: Sequence, Spawn, Repeat, Reverse Ease Actions: Exp, Sin, [...]