Crashplan has a home plan that lets you back up unlimited data for all your machines. It works on Windows, OS X, Linux and Solaris, which is great for me; I back up all my machines to both the cloud and my Nexenta/Solaris NAS, as well as backing up the NAS. In fact, if you know other people who have lots of storage, you don't have to pay for Crashplan at all; you can back up to them, with encrypted data.