Dar is a shell command that makes backup of a directory tree and files. Its features include splitting archives over several files, DVD, CD, ZIP, or floppies, compression, full or differential backups, strong encryption, proper saving and restoration of hard links, extended attributes, file forks, Door inodes, and sparse files, remote backup using pipes and external commands (such as ssh), and rearrangement of the "slices" of an existing archive. It can run commands between slices, before and after saving some defined files or directories (for a proper database backup, for example), and quickly retrieve individual files from differential and full backups. Several external GUIs exist as alternatives to its CLI interface, like kdar, DarGUI, SaraB, etc.
rsyncbackup is a handy tool for scheduled backups using rsync. rsyncbackup lets you easily setup multiple source folders and destinations, both locally, on your iPod or external firewire disk, or at a remote destination using ssh. rsyncbackup has no GUI, but is based on editing configuration files. The script is meant to be run in a crontab, so user interaction is not neccesary. Basic terminal skills are required to use the program.
bdmn is client/server-oriented backup system. The daemon runs on the machine being backed up, and the client runs on the machine that stores the backup. It is very simple, but very fast. It only uses tar, gzip, uuencode, and Perl, so it is portable to many operating systems. It includes a very simple access control system for itself.