- Cocos2D is the framework for 2D games
- Chipmunk is a physics engine written in C
- Box2D is a physics engine written in C++
I will be using just normal cocos2d as I plan to make a puzzle game, so I don't need physics or anything like that. This is also a good idea if you want to use a Pokemon like game or anything like that. If you plan to make a side scroller you will might want to use Chipmunk but it can be complex in places (I've had a look into it). You can make a side scroller in cocos2d and implement gravity rather simply, so don't think you NEED to learn chipmunk.
The latest version of cocos2d is out, so be sure you have the latest version and have it installed. You can find out how to do that here: http://www.cocos2d-iphone.org/wiki/doku.php/prog_guide:lesson_1._install_test
I won't be documenting how to make a game from scratch, I will just be blogging my progress and solutions to the problems I face. So its up to you to go off and learn bits yourself. Youtube is a great place to start.