Ever wish you could set up a small, efficient server? Maybe you're setting up a mail server for a couple of people, or something to hand out music files over a home network. Do you really need a full-fledged PC with a noisy fan, sucking down 100 watts and heating up the room?
Fortunately, there's a class of computers ideally suited to that sort of job: "plug computers", sometimes called Sheevaplugs after an early model. The whole computer is built into the bit that plugs into the wall, so they're barely bigger than a normal "wall wart" power supply. They use power-efficient ARM CPUs, so you can run a server with only 5 watts. They're inexpensive, usually just over $100 for a plug with 512M RAM and 512M flash. Best of all, they come with Linux installed right out of the box.