Sync2s3 - Backup your files to Amazon's servers

I have not tried this but it looks very interesting.

Sync2S3 synchronizes your files with the Amazon Simple Storage Service (S3), providing you with a secure and affordable backup solution.

What is Amazon S3?
Recently, Amazon launched a new web service which offers you unlimited storage capacity at an incredible price. By synchronizing your hard disc with this storage service, you can keep secure backup copies of any file below 2 GB.With Amazon S3, your data is stored in a highly scalable system, which is mirrored in several storage centers around the world.

Is the file transfer to Amazon S3 secure?
With Amazon S3, all file transfers use the most comprehensive security available.
First, a secured internet connection (SSL) is used to connect to Amazon.Then, every single request to Amazon is encrypted with a 'private-public-key method', which means that even the correct time is necessary in order to communicate with Amazon S3.
Sync2S3 takes the built-in security of Amazon S3 one step further: Every file is zipped and encrypted with a 256 bit AES key.A normal, password-protected zip file can be opened and accessed fairly quickly. With a so-called brute force attack, you can try approximately 5 million passwords per second.
With a 256 bit AES encrypted zip file you can try only 70-80 passwords a second. This means that you need about 6.5 million years for an eight character password – which should be secure enough for anyone.

How much does it cost?
Amazon S3 is incredibly affordable:
0.15 USD per GB per month of storage used0.20 USD per GB of data transferred
If you want to use Sync2S3 with this service, you have to pay an additional 29.95 USD.
Let's say you want to back up 10 GB. How much would that cost?
For one year it would cost you a total of 33.45 USD!

How does it work?
First of all you download and buy Sync2S3.
Then, you sign up for the Amazon Simple Storage System (S3). You can use your existing Amazon account.
Finally, you start Sync2S3, select the folders you want to store on S3, and start the synchronization or backup process.

http://www.sync2s3.com/