Our number-one-software is Yadis!. It's an easy-to-use backup-tool, which will save you a lot of troubles. It guards your personal data by making real-time copies (whenever you make changes to your documents) to almost any destination you choose. You do not need to shedule! Whenever you make a change, your data is saved. If the backup destination is not available then the backup is postphoned untill the destination becomes available again.
See also: free real-time backup tool, easy, simple, small, portable, removable device, network, backlog