Web 2.O for teachers

Just attended a worskhop and identified a couple of interesting sites that can be used for effective teaching and learning...

And here are links to some of the most interesting sites that were shared:
http://chinswing.com/
http://livemocha.com/
http://zamzar.com/
http://www.edu20.org/ (An Learning Management System)
http://www.toondoo.com/
http://edublogs.org/ (A blogging platform for educators.)
http://teachertube.com/
http://merlot.org/