revolutionizeed:

Wall Wisher – Like collaborating with virtual post-it notes on a virtual wall. It really has lots of uses. There are so many ways to incorporate Wall Wisher in the classroom. Make sure you take a look.

I’ve always liked Wall Wisher and some of these other sites are great as well.  Looking to try out Titan Pad soon in my classroom!

Ten Sites Supporting Digital Classroom Collaboration In Project Based Learning