Vagrant for Virtualized Environments
One of the goals of a system like this is to encourage "good behavior" by making it easy to follow good practices. Testing and automation are some of those good practices and Vagrant (http://vagrantup.com) is a tool to help them. By being able to quickly spin up and tear down VMs, Vagrant encourages rapid (continious) deployments for testing. Developers can also use Vagrant to maintain individual and separated development enviroments.