Infrastructure as a Service (IaaS) is the delivery of computer infrastructure (typically a platform virtualisation environment) as a service.
The now de facto standard of IaaS providers is Amazon with their EC2, S3 and other web services. I have created several Linux AMI (Amazon Machine Images) that are automatically configured using Puppet manifests. This allows the activation of as many server nodes as required within a few minutes, whether you need 15 or 15,000.
Many IaaS cloud providers are now supported by the libcloud library. I have developed several deployment and manual scalability scripts utilising this library. It allows high level abstraction of common cloud provider operations and processes such as starting/terminating instances to creating new instance operating system images.
