Carbonite - great if you're running Windows
Let's not forget that Carbonite runs only under Windows (incl. Vista). A solution for the Mac was due "mid-2008", but still hasn't arrived, and there's no sign that it'll ever work for Linux or (non-Apple) BSD users.
Linux and BSD/MacOS users can use a different solution, using Amazon's S3 storage mounted as a filesystem using "s3fs", plus standard backup tools like BackupPC.