browned:deadlyllama: If you want something a bit more DIY, I use backupsy.com. Essentially you get a VPS you can install your own OS, backup software, etc onto, and if you wait until they next offer a deal on lowendbox.com, you can pick up 500GB backup storage for 7USD/mo.
I run linux and Bittorrent Sync on mine and put Bittorrent Sync on various family members' computers. Much cheaper than 5USD per PC. Even my mother in law's photos are backed up now!
Looks like they have a 40% off for life coupon on their website right now.
When they have one of these specials, it's even cheaper: http://lowendbox.com/blog/cloudive-7month-2gb-ram-ssd-kvm-backupsy-7month-500gb-kvm-vps/
EDIT: looks like that SMOKING discount code is still valid.
If you pay them USD2/mo more, they will let you host non-backup stuff on the VPS, too.