Ok I have to say that I am partial to some hosts, especially wordpress and wikispaces, but this one is a great wiki for teachers. Wetpaint offers simple tools for creating a classroom wiki. Wetpaint offers various site schemes and templates and if you were to choose the classroom option, all navigation and pages for class syllabus, assignment, announcements and more are created for you. A great feature for the busy and novice wiki educator. I would now recommend this to you over wikispaces since it is easier to create a true classroom wiki or web site. Did I mention that you can email them to request an ad free site. Give it a shot and share it with every educator.
