I use an automated backup system which backs up specified directories overnight. I only backup personal data, i.e. the stuff which I can't replace. It's backed up to a NAS device, and every week or so I backup the backups to a USB hard disk. The program I use is one I wrote myself years ago, called backerupper. It's still available on Sourceforge if you're interested, but I'm not in a position to develop it any further.