How can I backup my NAS? What software?

Hello -

Just made the jump to a MacBook Air and LOVE it!

I keep my files stored centrally on a home NAS so that I can access from the MacBook or from the few pc's in the house.

What's the best way to backup from the NAS? I could backup from the NAS to local storage, but that's backwards as far as tools like time machine are concerned.

Any thoughts on what software would be best to make regular NAS backups?

Thanks!