Depends what you want it to do...
A project I have been working on for a while now is to replace my firewall/bastion host/QoS/blah blah utility box with a low power replacement.
Currently it is a 233mhz box with 64mb of ram, it has a 200W power supply, but probably only draws 20ish watts on average.
The plan is to replace it with this:
At peak it draws 5W, and should average about 2-3W draw, it is 266mhz and has 128mb of ram. It will run OpenBSD, which my current firewall uses, but I am going to mount the filesystem in memory so I do fewer writes to the CF card.
It's also the reason I haven't written the pf guide yet, I am going to make some significant changes to my current setup... I'll of course post on it (and take more pictures) as I go. This weekend is a long one, I will try and work on it.
-id