CDBKUP is a professional-grade open-source package for
backing up filesystems onto CD-Rs or CD-RWs.

Features:

Supports full or incremental backups.
Results are stored as GNU tarballs on ISO 9660 filesystems.
Excellent support for multi-session CDs.
Large backups can be split between multiple CDs.
Supports gzip, bzip2 or no compression.

WWW: http://cdbkup.sourceforge.net/