My 12 year old son and I built this little super regenerative receiver based on  the one tube emergency receiver article below (the last 2 pages).  

Most of the components were made from a odds and ends found floating around my shop. The radio uses a 1S4 tube (careful - the 1S4 pins are different than the 1S5 tube, which is harder to get), with a 1.5V C cell for the filament and a 3x9V batteries in series for a B+ of 27 volts. We further modified the original design to accept a crystal earphone, since 2k earphones are hard to come by.  For this we used a 2K2 resistor in parallel with the crystal earphone to simulate the original 2K headphone.

The radio works well with a 30' antennae, picking up several stations.  It receives the local station with a 5' piece of wire.