Make a key out of any thing. Literally. Banana piano? No problem. Play dough. A pencil sketch. A beachball. Connect any and all of it with an alligator clip and you have an input device. Any material that has even the tiniest bit of conductive capability can be a touch sensor with the Makey Makey. The Kickstarter project goal was $25,000 and it raised $568, 106 from 11,124 customers in 30 days.
Make + Key = Makey Makey. It has a fun ring to it, but more than that it is a powerful way to get kids engaged in learning about inventing, and tinkering, and making interesting projects.