Editing my answer a bit to reflect what I believe the spirit of the question to be.
This one, a gardening forum, a dance forum, a chihuahua forum, a Naranon forum (for the loved ones of addicts) and a private forum I created and webmaster so a bunch of friends from a previous abuse forum can stay in touch. I'm registered on several more but don't visit as much as these I mentioned.
I'm also on facebook, and there are a number of private groups I belong to there. An abuse group, a post-abuse group, a loved one of addicts group, a wellness for women group, a dance group and half a dozen buy/sell/trade groups for my neighborhood and general part of town.