winter project: home server

Hi,

First:
@home, i use a HP xw6600 as server. This one uses more power than i like...but it has the power to virtualize, and thats what i needed...

So, i think at the moment about building a home server, from industrial standard components. I am here to search about recommendations...

This should be possbile, and i think this could also get a interessing project for public, as an "equivalent" to olpc (one laptop per child).

The server should be able:
- to have an absolute minimum on power consumption (5 watts would be well, i think...)
- to use as less space as possible on the desk.
- it should be able to run virtual servers (4 is optimum)

as told, it is a home server, and most time of the day, he can be bored. Nevertheless, there are few cpu-consumpting applications like virus check, spam check on postfix, postfix, cyrus, webserver, database server, dansguardian filtering, squid and others on low consumption like samba :)

it is possible to have disks external (usb or whatever) and have the system e.g. on memory cards.

Target OS should be Fedora of course :)

So, anybody here to discuss advantages/disadvantages and hardware proposals?

Cheers,
Roger