CrashPlan is a backup service where you can have unlimited space, and backup past versions of your files as well!
Their services (such as very intuitive and capable software & developers, and a very handy App), are definitely the best I've found
among the known Backup services (Mozy, Carbonite..).
Anyways, for Black Friday they had a special sale
(they still have it, only the discount is not as big) and I basically got
a 1 year Family Package (2-10 computers) for absolutely Free!
Try out CrashPlan, they also have a free version if you want to backup between computers.