I created a Wiki at ideas.rotundus.com yesterday, with the idea of using it to organize my bookmarks amongst platforms and also for a little bit of scheming and plotting regarding some of my ideas (eg. the Google Maps idea mentioned a while back).
At the moment the access policy by default offers access only to myself on all pages by default making it a little less open than many wikis that I've observed in the past. One interesting thing is that the access control policies also apply to things like the login page. When I had originally set the access policy to give access only to myself, I was actually prevented from accessing the login page in order to login to the system (a little database hacking fixed that).
The software package that I've chosen to use for my new wiki is Wikka Wiki. (Who comes up with such silly names anyways?)