I think wallwisher is a great way to poll the class. When the polling has finished, the information can be used/analyzed to put into graph form. Or it could be used as a way to get to know your students. I also think a tool like this would be helpful in getting the shy students participate and share their opinions and ideas. Using the computer means they don't have to speak up in front of their class.
I also created an account with Skype in the Classroom. I think this tool would be fun to use with pen pals. After students have been writing to each other for a while, it would be great to "meet" through Skype. Teachers also use Skype in the Classroom to set up projects. An example of a project is a teacher in a northern state is looking for a class in the south to share a project on the civil war. I hope that makes a little sense.