I want a small, easy to use wiki. One that anyone can post to (TiddlyWiki, last I looked, was one-person-edits, if that's changed then I'll give it serious consideration) and doesn't have the baggage of MediaWiki. Wikia is a no-go, because their ads are thoroughly obnoxious and I'd much rather self-host.
In more pertinent news: 7,500 words in 2 days. Beginning day 3.