Cloud Foundry is the open source PaaS offering from the newly formed Pivotal. It can be used to deploy your applications on a variety of infrastructures, including Amazon Web Services, OpenStack, and vSphere. It supports Java, Ruby, and Node applications out of the box, but if you're working with .Net, you can use Iron Foundry, another open source project built on Cloud Foundry.
In addition to the open source version, Pivotal offers a hosted version (currently in beta) that deploys your apps to Amazon Web Services where you can easily bind a selection of services, including MongoDB, RabbitMQ, and JMeter load testing. Enterprises are already paying attention: GE, IBM, Intel, and Baidu are among those that have already adopted the software.
-- Jonathan Freeman