I've used several:PBworks
is a straightforward do-it-yourself wiki. You manage everything and have to build everything. That provides plenty of control, but it can also get time consuming, and if you're not savvy in the ways of html and crosslinking it could be slow and frustrating. Here's an example of an old d20 campaign, in a homebrew world called Fayteri
that used it for plot and loot tracking.
Obsidian Portal is more dedicated to RPGing than PBwiki, though this has its ups and downs. You know where to find it, and there are ample campaign sites to surf around on. I play in an OP campaign currently, using the Rise of the Runelords
adventure path. I feel like OP could be better, but it's in the center of the space for this kind of thing, and that's hard to argue. I *do* like the ability to "fan" a campaign, since surfing around the heavily fanned games can be a lot of fun--some guys work really hard on their campaign sites, and it's nice to have a way to point that out.
My current favorite in this arena is Epic Words
, wherein I'm involved in a Curse of the Crimson Throne
campaign. It's still got warts--no engine is perfect, but these guys seem to be more engaged in actively working on the site than the Obsidian guys. Of course, I'm a sucker for the underdog, and Epic Words is certainly the underdog versus something like Obsidian Portal, so take that as you will.