I use Mozy to back up all of my Scrapbook files. Just like Lisa said with Carbonite, the first download takes a long time, but after that it is done quick and you don't even know it is happening.
There are coupons out there online for both of these sites. I pay $4.95 a month for mine, but of course like everything if you pay for a year it is cheaper.
Good luck, let us know what you find.