The NSLU2 from Linksys is a fantastic accessory for any home user to have attached to their network. It is a way of connecting any external hard drive (be it a HDD or a memory key) to your network, allowing it to be accessed from anywhere. More here
The greatness of this little device however, expands ten-fold when you replace the official firmware with any of the multitude of replacements available for it. If you’re still using the official firmware and you’re happy with it, that’s perfectly fine, but if you’re looking for a little bit more, take a look at the offerings available over at the NSLU2-Linux site.