This LaCie external hard drive is a lifesaver is easy to use. Plug it in, back up your stuff, and voila, done! It takes firewire or USB and is designed nicely, not messing up the visual of your workspace.
Having an external hard drive is essential to keeping your data protected with regular back-ups. I have Apple's Time Machine set up, all I have to do is plug the USB into my Macbook Pro daily and no worries. It's super quiet save when it first turns on, but hey, you know it's on then. 500GB isn't too shabby.