Webducates’ Dragster fits the bill as a EDU 2.0 app. Check out this example activity where users can not only classify existing topics but add new ones as well. The emphasis here is on the fact that this activity can be completed by multiple users asynchronously.
I am going to use this for team brainstorming/mindmapping. As a generative learning approach, wouldn’t it be great if you could click on a topic to a mashup page where ppl could contribute their resources and integrate their perspectives into a wiki…