Amazon Web Services
Main site: http://aws.amazon.com/
Console overview, tour, all categories of info: http://aws.amazon.com/console/
For example, Amazon EC2 Features at http://aws.amazon.com/console/#ec2
I watched the EC2 tutorial at http://d36cz9buwru1tt.cloudfront.net/console/AwsConsole.html
AWS Documentation: http://aws.amazon.com/documentation/
EC2 Documentation (Getting started (recommended), user's guide, etc.): http://aws.amazon.com/documentation/ec2/
Go to http://aws.amazon.com/ and click on the button which says Sign up for a free Amazon Web Services Account – Sign Up Now.
You can use your existing Amazon customer account email and password if you already have one.