Educational Wiki: http://educationalwikis.wikispaces.com/Articles+and+Resources
Relevent sites found using a google search of the keywords: 'wiki's in k12'
http://wik.ed.uiuc.edu/index.php/Wiki_in_a_K-12_classroom - discusses ways to use wikis in a k12 setting
http://wikisineducation.wetpaint.com/page/Teacher+Peer+Wikis - list of wetpaint sites being used by teachers in many content areas
Site created by J.Bodenhamer. Users can post, edit, and review materials without having to register their e-mail address. This would be appropriate for rural schools whose students have limited or no access to the internet outside of school:
I had my 4th block class use the wiki today, they seemed pretty exciting by the concept. We are going to collaborate on tying the unit standards to the materials covered in class to show the connection between the text to the standards and the text to world.
Applied Math Wiki Solutions Manual: http://am40s.pbwiki.com/