Cocos2d-iphone is a framework for building 2D games, demos, and other graphical/interactive applications.
It is based on the cocos2d design and it uses the same concepts, but instead of using Python, it uses Objective-C.

Paulson App – a great blog showing how to build a small game containing, main character,
enemy sprites, collision, scoring and parallax scrolling.

A must-see for beginners.

Tiled is a general purpose tile map editor. It functions as a free tool to allow the easy creation of map layouts.
It is versatile enough to allow specifying more abstract things such as collision areas, enemy spawn positions,
or power-up positions. It saves all of this data in a convenient, standardized tmx format.

Use Zwoptex to create sprite sheets in just a couple of clicks. With powerful features,
super turbocharged algorithms and an amazingly elegant interface sprite sheets could never be easier.