Now here's a fantastic tool, although I must warn you the interface takes a little getting used to.
Debategraph is a brilliant idea for taking Wikis to a new level. As you may know, Wikis (of which Wikipedia is the most famous) offer anyone the chance to contribute to a body of contextualised knowledge on a given topic. The problem is that sometimes it becomes too difficult to absorb all the different points and links that end up in a publicly edited web-based document.
Debategraph tackles this problem head on by allowing users to create easy to read visual maps. These show the different points made in a discussion. Various colours show whether or not someone is agreeing or disagreeing with a particular point. Each point is represented a sphere.
By clicking on a sphere a user can open up more specific elements that follow that line of the the argument.
It's a fantastic resource and I'm tempted to try it with one of my English or Classical Civilisation classes.
Do be aware however that (a) there doesn't seem to be a way of making a debate map private, so anyone might see what's been entered. This raises issues of student ID privacy, but on the other hand does mean you might get more input from around the world, which could make for an interesting exercise; and (b) the interface isn't as intuitive as it might be when it comes to entering data.
All of this points to how the nature of data sharing, analysis,. and knowledge capital is being altered at a remarkable rate. The challenge for teachers is to figure out which parts will work and which parts are best left beyond the school gates.