Regularly $50/year, but to classroom teachers, it is free. You get a free wikis space with zero adds, no usage limits, and great support.
This is a pretty neat tool to use in class because you can create individual student accounts so that they can contribute on a highly monitored and permissioned level. You can increase student groups ability to collaborate by creating group accounts or pages for classroom projects.
Great opportunity to get a free account at ClassTown.com. You get Blackboard-Style message boards, printable worksheets, newsletters, private messages, and photo and video sharing.
ClassTown's goal is to ease the burden on teachers and to help them use more technology in the classroom.