Jenkins Bootstrapper for the EC2 Cloud
ci-infrastructure uses Chef driven via littlechef to make the setup as painless as possible. You fork this project, configure your ec2 credentials, configure your SSH access and then you're a couple of commands away from a maintanable CI setup that you can use to make your software more awesome.
The process starts with an optional fork of the repository, an installation of Chef and Python requirements, and then you go on to launch your EC2 node and make configurations to your SSH, littlechef, and Jenkins.
Check the project out on Github.