The free open source Cocos2D game engine is something that is searched for and talked about alot on this site. I occassionaly receive questions about the engine, and most often I’m asked about beginner tutorials. Typically I’ll just reply saying to go through the example, and I think that’s a great way to learn how to use the engine. Many great examples are provided, and if you really want to understand the question going through the examples systematically will teach you the ins and outs of Cocos2d programming. That being said I’ve found this tutorial that does an exceptional job of showing you the absolute basics.
In the tutorial Ray goes through the creation of a simple 2D shooter. Specifically, downloading and installing Cocos2D, using the Cocos2D application template, adding sprites, moving targets, shooting projectiles, collision detection, and other game creation essentials in a step-by-step fashion.
[source Ray Wenderlich]