How can I remotely upload files to Amazon S3?

I am looking for a way to transfer files from a server to Amazon S3 bucket, without f开发者_如何学Goirst downloading the files to my computer. All of the files I plan to transfer can be accessed publicly (e.g. http://something.com/file.ext). Everything I tried only allows me to directly upload files from my Mac to S3.

P.S. Although I have access to windows, a Mac app that can do this would be great... or maybe a browser-based solution :)

You can check out this PHP class (and a net tuts tutorial on it), it works well, I've been using it for a while now. It includes bucket creation, deletion, adding files and more. You can easily add files remotely from another server, or from the same server you're running it on.