I don’t, myself. However, I was skimming through the board at Ghastly’s Ghastly Comic (warning: NSFW) and I ran across our very own Lynn Bodoni. If I post the link here, it redirects to microsoft.com for some dog-ass reason.
So, do you or don’t you?
Yes, I must admit that the SDMB is not my only mistress. I’m also a presence at MadonnaMad’s little haven. All my old friends from the old Madonna dotmusic board are there. We’re a funny little hed, we all went from dotmusic to Madonnarama (RIP) because the mods were better, and when 'Rama shut down we were scattered until we found MMad. Good times. le sigh
I routinely post on several MSN and Yahoo boards, as well as some gaming boards.
I used to post a lot at grammarlady.com, but with all the time I spend here now, I’ve been on a long break. There are a few newsgroups I used to keep track of, but they got annoying – I much prefer moderated groups.
The typical SDMB response:
“There are other message boards?”
But seriously, yes. I’ve been posting on FARK lately (registered when I couldn’t stand lurking any more. . .love the PS contests). I also post (rarely) on the message board of the St. Louis Post-Dispatch, on Weimaraner boards, and various train-related boards.
I co-administrate a small forum on EZBoard (50ish posts a day) and post to another one that is basically its sister board. I’ve been posting with those guys on five different boards for three years now, so we’re a little close.
Other than those two, the Dope is my 'net home.
I also frequent my online gaming guild’s board, as well as several other EverQuest related boards.
I randomly insult people at various music related boards. Don’t know if that counts.
But SDMB is the only board I truly care about.
Yep. I post to the Trillian boards from time to time. I also post to the Elder Scrolls III: Morrowind boards, but that’s pretty infrequently. That’s pretty much it.
Only other message boards I post on are Fat Cat Club, and Something Awful.
There’s two boards that couldn’t be any more different if they tried.
I’m also on a couple of gaming boards and post occasionally on the FFF.
I was monogamous for my first two years as a doper. Recently, however, I’m moved out to discussions at various sceince fiction/fantasy related boards.
I try to limit myself to 5-10 boards at a time. I think this was the fourth or fifth board I was ever on, and I’ve joined many since, although I’m not active on most boards I’ve joined.
I post over at the Bad Astronomy boards fairly often.
I saw the same thing.
I tend to browse through the forums of a few comics that I look at. Other than that the only forum I visit is somethingawful.com
I manage (think Ed Zotti’s level) a big-ass community for a for-profit niche market website, owned by a major corporation, with about 10,000 posts a day.
The only place I come for fun is here. Wheeeee!
Twiddle
I started wandering around the Fabulous Forums of Fathom when the Dope was tanking so much at the start of the upgrade, just for a fix, since (a) I wasn’t on any other boards, and (b) there are a lot of Dopers who also hang out there. I like the place – it’s enough like the SDMB to be easy to get into, yet different enough to make it interesting. It’s also more welcoming of game threads, perhaps since it doesn’t have the overload problems that the SDMB faces.
I’m also a member of a Yahoo one-list group that’s been together, in various incarnations, since 1998, and has become a tight-knit group of friends. We six current members (all part of the founding group) try to have a real-life get-together at least once a year. Which can be difficult, seeing as we’re residents of Massachusetts, New Hampshire, Ohio, Delaware, Illinois, and Walkerton, Ontario. 
I post fairly regularly at the Japan Today message board (same username), but traffic there is a fair bit slower, so I spend most of my time here.
I won’t out anyone, but I’ve also encountered fellow Dopers over there.
Well, a board called Teenspot. I actually am on the staff there.
When I played Dark Age of Camelot, I used to post all the time at the Camelot Vault boards.
My other main posting forum for now is the Fantasy Football Today main board.
Yeah. Lame, I know. Straight Dope is where I get my intellectual fill (although the math and conspiracy on the Camelot Vault boards were occassionally impressive)