A question about home backup software.

At home (Windows Vista, XP and a SUSE file server for sharing files between them all) I backup all my user files, application data and stored files with basic scripts to an external eSATA drive. Does anyone use any FREE software that they are happy with for backups? Not the “free” stuff that comes with a drive you paid over $150 for…I mean free to download. Thanks in advance for your opinions!