Dabbleboard is a free basic Web 2.0 tool. Web 2.0 tools are part of the read-write web, meaning that you can read the website and also add to it, or write on the page.
This site is a combination of a mindmapping tool, a collaborative tool, and something that you can learn in 3:50 minutes in the tour of the website. Here are some ideas to get you started using Dabbleboard in the classroom - both for instruction and for student projects.