I did a bit of research when I was trying to get an off site backup up and running... in true nerd fashion I ended up building my own via a VPN connection to a server at our other house... nevertheless, there are some great options out there.

There was something about mozy that just kind of rubbed me the wrong way. I hear good things, but I'm not 100% sure I trust their security.

An option I really liked was Amazon's S3 storage and an application called Jungle Disk (http://www.jungledisk.com/ )... its a two part solution where you get an S3 account that charges based on the amount stored and your monthly transactions (there is a chart on the JD site above that shows examples) but for most folks it should be less than $10/month. Jungle disk takes care of the backups and encrypts them as it goes so you know your data is safe, even on Amazon's servers.