Hi James,
Force.com for Amazon Web Services includes two main components:
Access to Amazon Web Services S3: This component exposes the AWS Simple Storage System (S3) services natively in the Force.com environment. Apex code wraps the S3 API and access methods, making them directly available to your own application code – enabling application flows in a discrete and semantically rich fashion, including the ability to automatically add, remove or modify S3 objects based on workflow and data changes in a Force.com application.
Access to Amazon Web Services EC2: This component is represented by pre-built Amazon Machine Images (AMIs) that have the full development environment necessary to extend Force.com. This includes language runtimes, configurations, and connections to associated API libraries,. Developers can use EC2 to simply instantiate the AMI and immediately begin development, without any additional configuration or installation procedures. The first AMI being made available is to use PHP with Force.com.
What all you need to do is, get the Amazon wsdl file and parse it in your Salesforce. This will create stub class in your Salesforce org. and then You can use this class methods to integrate your Salesforce with S3.
Thanks.