Google Hangouts now offer screen-sharing, a sketchpad, and integration with Google Docs. That means that as you collaborate with others, you can view each other’s desktops, you can view and edit documents together, you can scribble and share notes.
This happened a few days ago, but is still important. I’m hoping Google will put Google+ in a position where you can use it as an App in an educational Google Apps rollout (a la Blogger, GMail, and Google Docs for example). That way you could have a Google+ network just for the students at your school.