Flickr

I think it would be fun to have a set of pictures on flickr that would correspond to a lesson. Then you could have each student make comments about the pictures you posted. You could even use pictures from a previous school year to help explain the steps in an experiment that they are about to complete. Sometimes visuals make things easier to understand. It would also be great to use the map section for a history lesson. Then the students could click on a location and look at a picture that corresponds with that specific location. A class photo album would also be nice for the students. They could help you choose photos and write comments, what a great memory for the end of the school year.