So there's the archives category which Toujours and Team Fail linked to, which has 20-something boards in it. I think not all of them are visible to members, but they're supposed to be. Archives is meant to be publicly visible... also, the boards Toujours linked to that are "archived" but still subforums/places not in the archive category should probably be moved into it.
Then there's another category called "backups" which has 2349239481234 billion forums in it that I think is only accessible to admins. It's full of really random stuff like old forums that were "deleted" or merged into other things, stuff that's been discontinued but isn't appropriate for member viewing (T-Dome) and other mod boards and stuff. Here's one page of them in case anyone is curious:
There are like three more after that, haha. And those are just the ones that show up from the front-end, even more are visible in the forum editor page of the admin panel.
They're all a big mess because when boards change around here, every admin basically does different things. Some will reset the permissions properly, some will hide the board, some will move it into backups, some will move it into archives, some will move it AND change the permissions... you get the idea. :P