I am creating a web-based RESTful service and want to cloud-enable it for scalability. I don't want to get locked into one cloud provider though. I'd like to be able to switched between Go Grid or Amazon EC2, etc. as pricing and needs evolve. Is there a common API to control the launch, monitoring and shutdown of cloud resources? I've seen Right Scale, but their pricing is just from another planet. Similarly, is there a common API for cloud storage?