I've been hanging around at the flightinfo message boards for around a year and it's gone steadily downhill. Although there are some good, informative threads, you have to wade through a whole lot of name-calling and flame-baiting to get to them. Airliners.net, despite a great database of aviation photos, runs a message board that's so stupid and juvenile that I visit it about once a year. For a great sardonic takeoff on it, visit airwhiners.net.
My buddy Glenn of RantAir recently started up an alternative aviation BB, called Got Wings? . So far we have like 7 members - mostly aviation bloggers - but Glenn and I seem to be the only ones doing much posting yet. I think this is a good chance for the budding aviation blogosphere to interact and get some good discussions going, beyond what we post in our blogs. So I'd highly encourage ya'll to sign up & start posting.