Matthew Russell has written a good introductory article to Cocoa for O'Reilly's Mac Dev Center that shows how to build a simple game board with pieces that can be moved with mouse clicks. It's good because it shows a simple and comprehensible graphics application without unnecessary complexity and with clear explanation. There is a link to the project code at the end of the article. Other Cocoa articles at O'Reilly can be found on their Cocoa Programming page.

Tags: Cocoa, Graphics