s3fs is a fuse filesystem that allows you to mount an Amazon S3 bucket as a local filesystem. It stores files natively and transparently in S3 (i.e., you can use other programs to access the same files). Maximum file size=5G.
"Recently, I have started backing up my servers to Amazon S3 (Simple Storage Service) using Duplicity. So far, I am pleased with the process and the costs involved. I still do regular disk dumps to my own backup server but may slowly phase down the frequency of these dumps."