Here are links to some of the best wikis that my students put together. They are somewhat in order of greatness. Feel free to browse through them to get a sense of what sophomores in a pretty good high school can do. These also present a great place to mine for projects that students can do. I became a big fan of the teaching wikis. Making the students put their own thinking caps on to present a project went a long way towards making them understand the material.

Atomic History Timelines
Energy or Water Wikis
Nuclear Power Point Part 2
Reaction Wikis
Gas Teaching Laws
Reaction Teaching Wikis