These are some demos come from the book 「Cocoa Programming for Mac OS X」 , and I will add more here.
Maybe your first Cocoa Program, use it to understand the MVC structrue.
Another easy demo.
#SpeakLine An interesting demo to translate text to sound, and remember last voice you selected(by userDefault)
#DiceView An interesting demo teach me the way to create a custom userControl.
#NerdTabViewController A demo teach me how to create a Tab-style view
wait more to come~~