Wikis are fun ways to share information. Of course, students are very familiar with Wikipedia; an article there will usually be the top result on any topic search they do. I have edited articles there before, very slightly.
We could adapt idea #2 where students compile a wiki for history of famous artists, architects, writers, etc. We could have used this for my high school's warrior peoples research project. The students could have created posts on their particular warriors and it would appear all on one page, rather than several individual pages. Plus they could post links to sites they used for their research for others to see.
I'd also like to see a wiki used as a way for students to review books they've read, create top 10 lists for books they've read or top 10 favorite authors, etc.