Who doesn't love the idea of a Hovercraft. This project requires 4 materials: A balloon, Bottle cap (that opens and closes, example water bottle cap), hot glue gun, and a CD.
Take the cap and hot glue it onto the CD over the hole. Place the ballon over the cap and blow the balloon up. Pinch the balloon until ready to let the air out and watch as it hovers around the table/floor.