Smallest web and E-Mail server, possible Linux or Windows?

[Linde]

I've got a Seagate Dockstar running 24/7 at ~15W to serve dynamic web pages, FTP, run an IRC bot, play music etc. They used to sell for like €20, but demand probably rocketed when people figured out they could run Arch Linux on it, so it's a bit more expensive now.

[Linde]

BTW, WebServUSB is just a software package, really. Seems like kind of a scam to me, since you could set up a portable LAMP on a USB stick yourself for a tenth of the price.