I have been a part of Replica Props Forums for many years, using the same name. That board has been a great resource for knowledge on building just about anything. And out of anything. There are a few professional builders among the community of hobbyists so their advise is incredibly valuable.
I have also been a part of Highlander Community For almost as long. I was a part of their old forums before they switched to vbulletin years ago. But I have not really had a lot of interest in anything Highlander lately so I rarely go there these days.
I suppose the Deviant Art forums would count. I have wasted a lot of time there too but that place is just too gigantic to actually know anyone. Hundreds of names come and go every single day.
I have been a part of a few more but never really posted more than a dozen or so times. Others forums I just lurked.
I've been apart of the ZeldaUniverse.net Forums. I've only been there for 2 years, (I've been there since 07, but I've actually active since 09.) That is like my home their. Everyone is nice nice, and I just love everyone there. I find everyone to be funny, and nice in their own way. I have a lot of friends, and there is great threads that I post in.... Well, sometimes.
I am part of other Forums, but I'm more fond of ZU. (And because I can only remember that one, unfortunately. :<)