Make a foxhole radio

Click on link in headline to watch video demonstration of a simple, or foxhole, radio made out of a paper tube, wire, paper clips, a razor blade, and a pencil. (Image via Boing Boing.)

From Bre Pettis in Make magazine:

During World War II, GIs in the field built really amazing simple radios to listen too. These were made with materials that they could get their hands on and were small enough to carry around in a big pocket. You can modify this design if you want to set it up so that it's tuneable too!