Here are some uses for old CDs. Some you probably know, some you may not have thought about.
The "perfect" set of coasters for any location. The coffee table, on a desk or at your workbench. If you want to get fancy, you can add felt to one side so that you don't scratch the surface.
Full length mirror
Sure you can pick up a mirror pretty cheap at Walmart, but will it start as many conversations in your dorm room as a mirror made of glued-together CDs? Use professional fingernail adhesive for maximum sticking power.
Old CDs make excellent Christmas ornaments and you're only limited by your imagination.