Marvell announced a $100 plug-in server this week. Plug it into the wall and attach the Gigabit Ethernet and you have a Linux kernel-based server with 512 MB memory and 512 MB storage. Five watt maximum power draw, always on, remote access to storage ... you get the idea.
A developer's toolkit will be released soon, so you can play with this fascinating hobbyist platform. Now you can host your own web site in the volume of a beer can.