I had a Pokémon fansite on MSN Home or whatever it was called back in like 1999, and that had a message board in it. There were also fits and starts with some homeschooling forums, where I posted once or twice on my mom's account. My first real forum, certainly my first Zelda forum, was probably Zeldaglitches.com, which died maybe a month after I signed up. My main one was Totally Zelda, which is still around (albeit untouched since around 2004 or 05) since ProBoards never takes anything down. (Anyone know whatever happened to the guys that ran TZ?)
Anyway, I also got onto the old forums that ZD shared with Zelda Legacy, as well as one other forum (Zelda Domain, I think, but I don't really remember; there's an off chance it was Zelda Universe). I didn't stay on those because I got into fights (One in ZD/Legacy's Mature forum, because I wasn't as mature as I thought I was, the other with one Maxine MagicFox of McLOZ fame because I hated her disabled right-click and because I was an overly defensive jerk about my own site).
I think I got out of forumgoing altogether once TZ petered out the second time, then eventually got back into it on PolyKarbon Art forums. I also joined Catholic Answers Forums like four years ago, but rarely post because it's just too big and fast-moving to keep up with. (Kinda like what Hylian Pants experienced: so many members, but I couldn't find a sense of community.) I joined BumbleKing Comics (home of Archie Sonic writer Ian Flynn) in December 08, then joined Zelda Dungeon's Dark World Forums (that is what they were called, right?) the following spring after giving up BumbleKing for Lent.
ZD is my most recent addition, and despite my having racked up a whopping thirty posts in over a year of membership it's my second-most frequented forum. A distant second. Yeah, BumbleKing eats up a lot of my time, probably because we get two new Sonic comics a month whereas we get a new Zelda game every year or two. Not that this is a good reason for me to be such a stranger here. I guess it's just the ol' short attention span.
Well, that's my experience with forums. It's been a longer journey than I thought. Shucks, now I'm feeling all introspective.