Web 2.0 Tools for Schools

I am a huge fan of harnessing Web 2.0 tools with students.  There are so many different tools available and the list keeps growing.  I will not even pretend to be able to keep up with all of them.  Cool Tools for Schools is a great wiki that has tons of Web 2.0 tools to use for teaching.  The list could be overwhelming, but I encourage you to find a new tool you can use with students to enhance a learning goal.