I've played for 10minutes with jotspot free wiki (sorry I wasn't able to find the “public permission” it looks like you cannot share with unregistered users). It looks nice, some features look really interesting like: form versionning. Some look scarry, like editing admin pages (I had a javascript in a textarea, ready to be changed !)
A lot of AJAX goodness, but It feels a tad slow --  perhaps it's the recent buzz generated by Jawodny and techcrunch ?
Anyhow, don't miss SocialText which is very nice.
