A German web retailer Manufactum recently put on it shelves a two pound mini-PC, they call Manuscriptum, that comes with a 500MHz AMD Geode LX800 processor, an 80GB hard drive, up to 1GB of RAM and a motherboard that takes up to four USB 2.0 ports. The VGA has a 1920 x 1400 resolution with a 2 x 10/100 Mbps Ethernet card. Naturally it has PS/2 and audio ports.
Run by Debian Linux, that bundles up a few start-up applications like OpenOffice, Firefox, Foxit PDF Reader, it is an excellent example of a “green” computer with a minimal consumption of just 12-watts.
The base price for Manuscriptum is €449, if you are not into Linux then you can stuck in Windows Xp but expect a different performance.
If you need a smaller Linux PC then go get Picotux, with its 3cm it is the smallest device with a Linux kernel (I guess)