BackupPC: a backup
system using rsync. Hard-links all identical files (even between multiple
runs and multiple backup sources), compresses the files, provides an easy
interface to find and restore files, etc.
drsync: a wrapper for rsync
that remembers file sets between invocations so that a 2-way synchronization
of two systems is possible.
rsyncbackup: a helper
script that uses config files to setup multiple backup scenarios and
invokes rsync (or rsyncX on MacOS).