I seem to recall that there was something on the world's smallest PC some time back, a web server was running on one. It was about as small as a pack of cigarettes or something.

Directron has an [link|http://www.directron.com/ezgo.html|EZgo] system about the size of a CD Player. Who says that PC companies cannot innovate? ;)

$748 with 1Ghz CPU, 20G HD, 256M RAM, Optional Components. But mix and match what you need. You will also need to get an external keyboard and mouse and a monitor.