EBWF was my main forum before its downfall (10k posts there) and I used to post a bit on Musicianforums (now Sputnik) which is quite frankly, inferior to MB
But I haven't visited either of those places in a long time.
Nowadays I only really post on MB and sometimes lurk on Talk Bass, Game Banshee, GP Forums (NZ forum), Television Without Pity and Anglotopia (pretty much dead). In fact, I don't even actively visit those... I just refer to them when I'm in the mood.