Nimbus is an EC2 implementation to provide compute cycles in the cloud for scientific communities. Nimbus is an open source toolkit that allows you to turn your cluster into an Infrastructure-as-a-Service (IaaS) cloud. NImbus provides:

Two sets of Web Service interfaces: Amazon EC2 WSDLs and Grid community WSRF
Implementation based on the Xen hypervisor (KVM coming soon)

Can be configured [...]