Links
Amazon S3
Amazon S3 provides a simple web services interface that can be used to store and retrieve any amount of data, at any time, from anywhere on the web.
The price for this valuable service is incredibly cheap.
Jungle Disk
Jungle disk provides a user friendly interface to the Amazon S3 cloud, as well as the RackSpace cloud.
By creating a virtual drive on your machine, which acts like any other drive, the use of the cloud is transparent.
JungleDisk also has simple, yet powerful tools for automating your backups.