==> Web Application Hosting : http://d36cz9buwru1tt.cloudfront.net/architecturecenter/AWS_...
==> Content and Media Serving : http://d36cz9buwru1tt.cloudfront.net/architecturecenter/AWS_...
==> Batch Processing : http://d36cz9buwru1tt.cloudfront.net/architecturecenter/AWS_...
==> Fault tolerance and High Availability : http://d36cz9buwru1tt.cloudfront.net/architecturecenter/AWS_...
==> Large Scale Processing and Huge Data sets : http://d36cz9buwru1tt.cloudfront.net/architecturecenter/AWS_...
These are the main usages a startup can make of AWS. Of course, depending on your core business, you will need to focus on specific parts.