This is a downloadable add on for Powerpoint that means that you can set up slideshows that can travel through the slides in any order and can zoom in and out on any of the slides. (This is a bit like the movement in Photo Story 3). Have a look at it on this video.
You do need to have Powerpoint 2007 or a later version but it will enhance story telling slideshows that your class make. Click here to go to Office Labs to download the application.