New
#11
USB external hard drive:
300GB - 500GB, Desktop External Hard Drives, Hard Drives, Components - Newegg.com
$70 or so for 500GB. Or if you have an available internal SATA port and mounting point for a second hard drive, you can just install a permanent internal hard drive for backup storage.
The problem with internet cloud storage is two-fold. The first problem is connection speed. How long is it going to take you to upload and then download a multi-GB image? The second concern is restoring in the event of a total system storage (hard drive) failure. What are you going to use to connect to the internet and the cloud storage location to retrieve the backup from and then install it on the computer?