Clonezilla is an excellent free utility that can back up disks or disk partitions (some of you may be familiar with Ghost). I use Clonezilla to backup my systems. To restore the disk on my netbook takes about 10 minutes and the saved image fits on a usb key.
Clonezilla can also backup to network shares, a small barrier to doing backups is having some media near to hand to boot the system from. So I have started adding an extra partition to all my systems that contains clonezilla so I can just boot from it.
Instructions on how to do this can be found at the Clonezilla web site¬†¬†One note, when you get to the update grub stage, dont be fooled by your Clonezilla option not showing up when the command runs. You should find that when you boot grub does show up option to boot from the clonezilla partition.