[ant512]

Try CrashPlan:

http://www.code42.com/crashplan/

It's free for peer-to-peer backup and is designed to do exactly what you want.

[slight]

Their cloud storage for backups is really cheap if you have a lot to back up and want them to handle your off-site too.

[chrisBob]

Thanks. That looks like a good fit, and the paid plans are probably less than I would spend on a set of external drives anyway. I will give it a try.