Amazon’s Simple Storage Service (S3) service coupled with Jungle Disk is an excellent, inexpensive solution for on-line backup.

The Amazon service is $0.15 per gigabyte per month, and $0.10 per gigabyte transferred. It’s pay as you go, so you’re never paying for more storage or bandwidth than you need.

Jungle Disk is a very user friendly front end for the Amazon service. It creates a new network drive on your system that is your access to your storage. Use it just like it’s a local drive in any application. It also includes a customizable backup utility that will backup at a scheduled time and keep archived versions of changed files. Finally, it’s free to try and only $20 to buy it. The license is for every one of your computers, including a USB drive friendly version that you can run on any system without needing to install it.