320GB NAS box (hang it off your home network). Compatible with Window, Mac, Linux (including Vista, no matter what eBuyer say).
Ideal for backing up your home machines (comes with software) and is a full DLNA Certified media server, so you can feed movies, music and pictures to a player (like the PS3). Will also act as an iTunes server.
Gigabit ethernet connection with two USB ports to hang extra drives off, or to act as a printer server to share your printer with everyone.
Can also be hacked in multiple different directions, with an active community. People have had them doing everything, up to and including being telephone PBXs. You can replace the internal SATA drive with something larger, if you want. See http://buffalo.nas-central.org
Bought mine for £80 only few months ago, and that was already reduced. Spend 5p on something and get free delivery.