I have noticed in my searches the Cocoa Touch for iOS seems to generate more community involvement. Perhaps I should focus on iPhone and iPad development instead. :)
Sites that I have found include but not limited too:
Cocoa with Love. -nice blog with good information; has comments enabled for feedback
Learn Cocoa - @cocoadevcentral.com has good basic information and examples; several good links to other sites but I don't recall any form of interaction such as comments or forums.
CocoaDev Forums - general forums, with wiki as main page supported by Panic (these guys produce some really useful software such as Transmit and Coda.
The Cocoa Programming Forum - very dated effort. Virtually no replies in first few pages of current posts.
Cocoa Community Forums - Nice forum where Admin, Darrell seems to make a valiant solo effort
Become an Xcoder - good pdf oriented to the beginner
Maybe I am looking in the wrong places but I haven't found any forums yet that seem to have a lot of traffic that produces many replies or help on posts. One exception seems to be stackoverflow.com that draws a wide range of programmers. I haven't posted there yet because it appears a little more advanced than my skill set, but I can foresee it being useful in the future.
These are the places I've bookmarked thus far. I'll surely add to the list as time goes on.
Anyone with knowledge of good sites for learning Mac OS programming feel free to chime in!