Here’s a nice little weekend project. You can pick up a barebone MSI Wind system (not the netbook, the desktop version) from Newegg for $140. It’s one of the first desktop systems to use Intel’s power-sipping Atom processor (1.6GHz). You’ll need to add RAM (it uses laptop RAM) and a hard drive (or CF card) to this kit, and maybe even a little Wi-Fi card if you’re feeling adventurous.
The board itself has an internal Compact Flash slot that shares an IDE channel, so you could stick a big CF card in there instead of a hard drive. That’s a nice touch right there. Maybe build a Car PC or something. There’s also a mini-PCI slot if you wanted to add that Wi-Fi card I mentioned in the previous paragraph. Might as well, huh?