I love Mozy. 2 gigs of backup for free, unlimited for $54 a year. The site is clean and attractive and the app is simple and unobtrusive; I never see it unless I haven’t backed up in a few days which rarely happens.
Last summer my hard drive fried and I didn’t even break a sweat because I knew it had all backed up automatically the night before. Made it easy to pony up that $54. The only drawback is that doing an initial back up of 10+ gigs could take an objectionable amount of time, but it’s a great system in combination with an external hard drive for your photo and music archives.
Check it out http://mozy.com