Here is a nice little video on how to create a Wallwisher. I've used this with great success in my classes for presentations. A student would present and the class would be at computer stations. Once the student completes the presentation, the other students post their thoughts on the Wallwisher. The presenter can then go back and see what student thought of their project. It is a great way for students to get instant feedback from their peers. Take a look at the video and play around with the site. I'm using it for the post above. Check that one out too.
P.S. - This was my first Screencast I had ever done. It was for my Grad class and it was easy to make after I got used to the set up. Enjoy!