Mike got it right with Carbonite, works great, but only on Windoze XP not Win 2k, so only one of my machines works with it. They are supposed to come out with a Mac compatible version next year, just in time for me to buy a Mac
My main large computer at the L shop has a raid array set up, similar thing to what Jeff described, I have two drives on the array, both mirrored so a total of 4 drives, I had to put a larger powersupply in the machine, but that was it, well the raid card too. Works well, I had the main "C:" drive fail last year, well one of them, I bought a new drive, installed it, rebooted, smashed the mirror, and then rebuilt the mirror from the undamaged drive, all if fine in the world.
I also have a large external HD that I back up to, and I have my photobucket page, plus I send most of my stuff that I'd be sorry to lose to my mother, she sends most of the pics to every other relation I have, and I know my mom backs up on CD as well. Perfect, no, it is not but I'd say it is pertty good.