More Etherpads

As I investigate further, I have come across more sites similar to Wallwisher. 
If you are looking for a way for students to collaborate on a project, here are some etherpad sites to try out.  They are easy to use as there are no accounts that have to be created, no user names or passwords.  Just share the URL.
Here are some ideas I came across on the Planet. Thanks Dennis Warren
An etherpad may be something useful:
PiratePad: http://piratepad.net/
TypeWith.me: http://typewith.me/
Sync.in: http://sync.in/
PrimaryPad: http://primarypad.com/