I am learning Cocoa programming these days, and am actually picking it up very quickly. As I have mentioned in the past, it reminds me a lot of SmallTalk programming. Below are some sites/resources that I am finding really helpful. I’ll update the list from time to time.
COCOABUILDER.COM - A perfect interface to both Cocoa mailinglists
MACDEVCENTER - O’Reilly’s Mac Developer page
COCOADEV.COM - WikiWikiWeb site for the developer community
COCOADEVCENTRAL - A site with great tutorials
COCOA FAQ - Frequently Asked Questions
STEPWISE - A classic site on Objective-C
HYPERJEFF - Cocoa Literature
REFERENCE LIBRARY - The official Cocoa Reference Library
MACRESEARCH.ORG - Macs for Scientists