Requirements
You will need to set allow_url_fopen to on your PHP settings. This option enables the URL-aware fopen wrappers that enable accessing URL object like files.

Known Issues
Some curl libraries, such as the one bundled with MAMP, do not come with authoritative certificate files. http://dev.soup.io/post/56438473/If-youre-using-MAMP-and-doing-something

Installation
- Download and install the Libraries (7.x-2.x branch) and AWS SDK modules
http://drupal.org/project/libraries
https://github.com/drucloud/drupal-awssdkv2
(For installation of awssdk, you will need to download the Amazon SDK v2 for PHP and place it in sites/all/libraries/awssdk )

- Configure AWS SDK

- Configure your bucket setttings at /admin/config/media/amazon

You can then:
- Visit admin/config/media/file-system and set the Default download method to S3
and/or
- Add a field of type File or Image etc and set the Upload destination to Amazon S3 in the Field Settings tab.