This forum is good. :D
http://forums.megatokyo.com is ok, it's kinda crazy but there have been some pretty harsh and obscene flame wars between a few people.
www.rpgamers.info is pretty good and pretty friendly
www.erality.com/rs is an excellent forum. It has a small membership but has never been far out of hand.
http://ariendor.net/ib is my forum...and it has had a few disputes between members in the past...but it has been going great for a long time now.
I've been part of numerous other forums...but I haven't visited them in a while now.