Kuro5hin (which I've diss'ed a bit in the past but not much) continues to be an extraordinary daily source of good content. This is probably one of the better articles I've read on Cocoa programming.
Cocoa is the native system for developing applications on the Apple Mac. This article introduces Cocoa and describes my experiences after about a year implementing a complex application in Cocoa using Objective C.
Read It: http://www.kuro5hin.org/story/2002/8/31/14253/3495