If you are itching to learn some basic game development techniques in Cocoa on Mac OS X, O’Reilly Mac DevCenter has part 1 of a series on building a game engine with Cocoa.
Matthew Russell leads you through the development of a Lines of Action (checkers derivative) computer game. In this first part he sets up the checkers board using a custom view subclass and provides all the source code. He promises to introduce some Artificial Intelligence in a later entry when he ads a computer opponent to the mix.
If you want a deeper look into game programming with Cocoa, I wrote about a book covering similar ground on my Make Mac Games site, a little over a year ago: Cocoa Game Programming Workshop.
Update (Jan 5, 2007): Building a Game Engine with Cocoa, Part 2