Here are two separate implementations of a quick-and-dirty file-level backup
system using shell scripts and rsync.

  rsync-push
     - used to back up a system to a remote machine using rsync.  Backup is
       initiated by the machine being backed up.

  rsync-pull
     - used to back up a remote system using rsync to the local machine.
       Backup is initiated by the machine storing the backup data.

I use rsync-pull extensively on my personal machines, and used to use
rsync-push on my work laptop (when I had one)