I think that a Wiki is a great tool. I know that i use wikipedia all the time. In my future math classroom, the students could use a wiki to share on a group math project. Where each of them had to do a different problem but the whole assignment was turned in as a group. Also, I thought this would be good for sports too. Especially when the kids want to get a party or dinner together. A wiki would be a great way to get the athletes and the parents communicating on the same page.
http://teachertipstraining.suite101.com/article.cfm/using_wikis_in_math_classes
I really like this wiki alot. First of all, for anyone that is unfamilar with a wiki and how to use it, this page gives a brief overview of what you should do. Math isn’t the easiest subject to incorporate technology into, so this page gives 7 or so different ways to use a wiki. Even if you already have a wiki for a specific classroom, this is another way to get more ideas