nffc's post asumes that the printer is plugged into a computer that is permanently on.
Alternatly you can buy
http://www.linksys.com/servlet/Satel...VisitorWrapper
something on the above page
e.g. PSUS4 and plug it into your router and your printer into the USB port on this and then the printer does not require a computer to be on for it to work. The PSUS4 is effectivly that computer.