S3cmd
Command line tool for managing Amazon S3 and CloudFront services
... (GPLv2) and is free for both commercial and private use. You will only have to pay Amazon for using their storage. Lots of features and options have been added to S3cmd, since its very first release in 2008.... we recently counted more than 60 command-line options, including multipart uploads, encryption, incremental backup, s3 sync, ACL and Metadata management, S3 bucket size, bucket policies, and more!