From what I've seen all other forums are dead apart from here. Why would you even want to go anywhere else than here?
I suppose that sometimes BCT gets a little boring; other small communities deserve a chance, too.
Boring? This forum is never boring. Always active and there's always drama happening every day. It's the only forum you can easily earn some bitcoins relatively easy. I signed up for a few forums when I first got into bitcoin but only made a few posts on them as this forum is by far superior in every way.
Also I think it attests to BCT's popularity that the OP is posting here asking where to find other forums. There may be other good forums, but if one (BCT) already has the majority of people, what would you think you would find at another one? Perhaps a friendly environment, but information wise I think this would be it.