The ability to scale your application on the fly to any level to meet the challenge of traffic demand. S3 is like the unlimited hard drive to store your data. EC2 is the virtual server that you use to run your business.

Here are the cost and the link to signup to begin using the service.

And here are the tools:

• Elasticfox Firefox Extension for Amazon EC2
• Amazon S3 Firefox Organizer
• Amazon aws console
• share ec2 image
• account activity report
• Elastic Load Balancing
  
  • $0.025 per Elastic Load Balancer-hour (or partial hour)
  • $0.008 per GB of data processed by an Elastic Load Balancer
  • Compare cost of a home server

The slideshow give you an idea how to set up an amazon ec2 and s3 and the cost of usage.