Just gave a enlightening talk on Box2D at the LiDG and have prepared a step-by-step walkthrough on creating a simple pinball game using the open sourced 2D physics engine! You'll learn the concepts of Body, Shape, Friction, etc. as well as how to build and run the Box2D engine for iPhone. By the end of the blog, you'll be equipped to create a basic working game in a couple of 100 lines of code! Don't forget to check out my slides and demos linked in the blog!