Mine is also ZD. I registered back in April, but I forgot about it 'till recently.
I registered in 2 other forums latter just because they require registrations to see links in the posts. And I'm kind of inactive there (only 2-3 posts).
My first forum was lotr.net. It was pretty good but the server had so many troubles. We even couldn't get on the forum for days sometimes and posts went through so slow or 13 times in a row
The site I'm the longest active at is narniafans.com (4 years now) because it is mainly the off topic part which is very cool or used to be cool. But since earlier this year I found this forum and I like it here
I think my first was A Sailor Moon Romance, back when it still existed. I've had several fandoms but haven't joined a lot of boards/discussion communities, to tell the truth. I was in a neopets guild for awhile but drifted away when I got tired of the site. This was the first one I'd joined - and stuck around - in ages.
My first and only other forum was Serebii, back when I practically breathed pokemon and all things related. If you've ever been to Serebii, you know it is huge! Was there a few years but stayed only in the Mystery Dungeon section where I made a name for myself as a moveset builder, but after my dad blocked my computer's access to Serebii for a few months on a paranoid fear of virus attacks I was never able to make myself return to that forum. Just too big.
ZD is the only other forum I'm active at, and I like it here, a lot. =D
Zelda Dungeon was the first forum I ever joined, and right now it is the only forum I have joined. Unless you want to count Gaiaonline. They had a forum, but I never used it, unless it was to sell an item to escape a 2% deduction fee for using the marketplace. If that does count, then my first would be Gaiaonline.
LOL oh gawd, for me, it's Naruto Froums, back in 2006... I have about 1,000 posts there. I've since pretty much abandoned the series, though.
That place is just.... wow. The hilarity of internet fandom at its best (or worst, depending on how you look at it) So many heated, pointless fights with strangers, endless pairing shipping, huge number of members yet hardly a sense of community. geez, I'm glad I left...
I got back into gaming about the same time I had kicked my anime habit, so I'm really only active on here and on ZU, which I just joined under the name Oggi. Believe it or not there is actually already a Hylian Pants on their forums!! D: I like it here quite a bit because of the politeness and the tight community
The first forum I had joined was long in 2001 and was quite popular. It was the My Nintendo Forums and it was a fun place where they had forum chats and all the good things you expect from a forum. It even had a mature section for the older people. Why, even in summer they had this fun little event called Camp Hyrule where you would participate in small forum games and chat with others until the camp was evidently destroyed by some freak event.
However, shortly after the Wii came out, the forums had closed and become this stupid tech forum. It is a sad fate for a once great forum. ZD almost felt just like it when I first joined.
Hmmm.... back in 1998, I joined Nintendoland's first forums and Zelda Power's forums on the same day. I remember I had a hard time deciding which I wanted to join, so I went with both. Nintendoland's community was much nicer and a lot more intelligent, but I ended up frequenting Zelda Power more because I had been with their chatroom pre-ZeldaPower (1996, I think?) and knew the community better. I enjoyed my time at both places, and I'd go back if they didn't turn out they way they are today. ZP has become troll paradise like ZU and ZI, and Nintendoland+Zelda just kinda died off. :<