I use a Mac and have a 500GB Time Capsule (also available in a 1TB). It wirelessly backs up every hour my entire computer, and I always have the ability to go “back in time” to find any file, photo, and even email that might have existed in the past. It can back up multiple computers (although I just use mine – my wife’s is primarily just email that is already back-up via our IMAP account).

Best of all, I never have to think about backing up anything – it all occurs automatically and without interrupting whatever I’m doing.