My employer has given me permission to open source the application that I developed to move our media to Amazon S3.
I think that it can be part of any solution that needs this functionality and I hope that the community finds it useful and contributes.
Find the source at Github
Here is the description from the README
Drop files on your filesystem and have them automatically uploaded to Amazon S3. S-3PO listens for files copied to a directory that you choose. The files are uploaded to Amazon mirroring the structure of your local file system. After upload the files are deleted, leaving only the empty directory structure in place. Errors can be sent to an email address if needed.