After reading a spate of blog posts on the topic, I’ve successfully launched a (bare bones) campaign wiki. I’m using Obsidian Portal, which is a free hosting site that’s designed specifically for roleplaying games.
My goal is to create entries for most of the major locales and characters in the game — and then include just enough content to get the players interested in contributing. Clearly there’s no guarantee that they’ll bite, but even if I’m the only one who ever edits the wiki, I think it’ll be a good tool to help me organize the campaign. The markup language (HTML and Textile, which I'm learning to love) is just complex enough that I could lose lots and lots of time tinkering with this site.