Many programmers find online mailing lists to be the best way to stay on top of what's fresh and new in the Cocoa community. In addition, they are an excellent place to get help on a problem; just be sure to search the archives first before asking!
Apple's moderated email list focused exclusively on Cocoa development issues.
Apple's moderated email list focused on Project Builder issues.
This mailing list is hosted by one of the premiere Cocoa development houses, The Omni Group. This list is open to a wide variety of topics for Mac OS X developers.
A source of news, information, updates, and special offers for Macintosh developers.
A browsable, searchable archive of Apple's cocoa-dev and The Omni Group's macosx-dev mailing lists.