Hip Hop Nexus :: Mainly hip hop discussion, but a fun community once you hang around for a while and get to know folks. When the e-zine portion of this page is functioning, I'm a regular contributor. I moderate the "Alternatives" board, but post frequently on most of the other boards as well.
Okayplayer :: Official site for a few of my favorite music makers (Common and The Roots). I don't often read all of the boards because they're so busy. I mainly stick to reading and occassionally posting in The Lesson because you can mention just about any music maker there and someone will share your interest (but the okArtist board is fun to read sometimes for the crazy fans and Questlove's occasional posts).
MFC Forums: The Cure :: Mainly discussion of The Cure. But there's an interesting cast of characters that frequent the place and make it a very fun board to read and participate in.
The-Breaks.com :: More of a reader than anything else here. I probably should be posting more, being that I'm in the company of record collector nerds like myself when I'm there. I don't know though, I usually spend most of my time there reading.
Music Babble :: Formerly associated with George Starostin's (great!) reviews page. Again, it's mostly overly analytical dorks like me babbling on and on about things you probably don't care about. I'm mainly a reader here as well.
Sound Circuit :: When this site had an e-zine portion, I was a regular contributor and I moderated the Respect My Mind board many moons ago (though most of the posters on that board wouldn't recognize me now). It's gone down hill, but it's one of the most popular and fastest moving hip hop boards on the internet with a killer design and layout.
