Cloud computing is often compared to the power utility model, but today's cloud providers don't simply supply raw computing resources as a commodity; they also act as distributors, dictating cloud services that aren't compatible across providers. A supercloud is a cloud service distribution layer that's completely decoupled from the provider. Leveraging a nested paravirtualization layer called the Xen-Blanket, the supercloud maintains the control necessary to implement hypervisor-level services and management. Using the Xen-Blanket to transform various cloud provider services into a unified offering, the authors have deployed a supercloud across the Amazon Elastic Compute Cloud, an enterprise cloud, and Cornell University. © 1997-2012 IEEE.