This is the only forum I'm on that I really talk on, I'm a member on a couple of others, but am not very active on them. And my user name is "edie" on every forum I'm a part of!
A Canadian Rhacs (mostly Crested) Gecko forum. Fantastic people, great community: http://www.rhacscanada.ca/
A (the!) harpists website/forum. Open to both amateurs and professional performers, and all people in-between. http://www.harpcolumn.com/
The best computer game guild ever! Various chapters organize into a large communities devoted to various MMOs, a private VENT chat channel for the best live voice chat while playing, etc. So much more. http://www.oldtimersguild.com/
A forum for guys (and girls!) who use straight edged razors. Its an art, and there are some really skilled craftsmen who open teach it to those who are interested. Best shave ever. (At least for me.) http://www.straightrazorplace.com/forums/
There are a few others that I drop into now and then, but overall, those are my regular haunts.
This above all: to thine own self be true,
And it must follow, as the night the day,
Thou canst not then be false to any man.