Here is forum about uses of wikis at Classroom 2.0. Classroom 2.0 is a free social network for those interested in Web 2.0 and Social Media in education.

This is ESL Wiki relating to the teaching and learning of English as a second language.

Here are some examples of wikis that have been used by EFL teachers with students. This should give you ideas of how you might want to use wikis with your own students.