O'Reilly Network: Building Online Communities
This is a great article. It points out many thngs that we assume or understand implicitly about web communities (such as people's sense of owenership of the community) but never say outloud ans sometimes forget.
Helping with a community just about to get off the ground, thinking about restarting an older one, and being part of the one that exists in the blogosphere, I'd have to say I'm a pretty active community participant, at least as far as building them. My contributions after that leave a little to be desired, but as long as others get something from the experience, it all works out.