Rightscale: EC2 Site Architecture Diagrams
http://support.rightscale.com/12-Guides/EC2_Best_Practices/EC2_Site_Architecture_Diagrams
The following diagrams will show some of the common site architectures in the Cloud. Depending on your computer resource requirements and budget, RightScale provides you with the flexibility to create a custom architecture that provides the necessary performance and failover redundancy necessary to run your site in the Cloud. Several of the most common architectures are described below. Use one of the setups below as a model or easily customize a setup for your own purposes.