Schtuff

Another wiki hosting service. This one appears to be ad free:

www.schtuff.com - What is Schtuff?: "Schtuff is the first to offer a totally free Wiki service. We've made the traditional Wiki easier to use, and tacked on a few really nice features like tagging, custom permissions, and an image gallery.

Schtuff is flexible. Use it to collaborate on group projects, create a blog, share photos with your family, take personal notes... the possibilities are endless! Have a look at some space examples."

via Educational Weblogs