I recently bought a 500GB Freecom NAS to replace my previous crappy IDE based 20GB one, and needed a way of making cPanel auto backup to it via FTP, say every sunday night. I came accross this site, within which the author has written a PHP script that connects to your cPanel installation and sends post requests with stuff like FTP server, name, password etc to the backup page - meaning you can set it to run on cron from within cPanel.
This is very useful, and I have it running up on my entire site at the minute. Via FTP it doesn't take long to send the 175mb backup through my ADSL line, probably about 15 minutes max.
It's worth noting this comment from the post - it shows you how to specify a remote directory for the backup (For my NAS it's /home/Backup/, / is disallowed).
