Sample Wikis gleaned from a quick search...
High School Science
Utilizes embedded glogster, links to outside sources, google calendar and online quizzes
https://urspace.wikispaces.com/

2nd Grade
http://mrsibrahim.wikispaces.com/

Primary Math-Global
http://primarymath.wetpaint.com/

6th Grade
http://b22geotopias.wetpaint.com/

MS/HS
Great use of video!
http://cyberclassroom.wetpaint.com/

Foreign Language
http://6thgrade-07.pbworks.com/FrontPage

Grades 3-4-Writing
http://terrythetennisball.wikispaces.com/About

8th-10th Computer Science
http://westwood.wikispaces.com/