On the Amazon AWS blog there's a recent post showing you how to sync data with S3 and handle multiple files quickly and easily.

Have you ever needed to upload an entire directory of files to Amazon S3 or download an Amazon S3 bucket to a local directory? With a recent release of the AWS SDK for PHP, this is now not only possible, but really simple.

He includes example code for doing it both ways - upload and download syncing - as well as some options you can use to customize the connection. You can define things like ACL settings, the number of concurrent connections and if you want the debug options turned off or on.