Syncato
Syncato is pretty interesting. It's piece of BlogSoftware which uses a native XML database as it's backend and is searchable via XPath. So the more you markup your text the more accessible it is. This is pretty neat from a blogging point of view, but from a Wiki point of view it's amazing. From a data management point of view (as opposed to a community point of view) this is what wiki's should be. Add a wiki markup to XML converter, RecentChanges and some sort of AccidentalLink generator and you have the best wiki ever.
Oh, and lets all remember that TheInternetIsShit.