Cohesive Flexible Technologies: Offers a “factory-as-a-service” where you can build virtual machines for various platforms (VMware, XEN, Amazon EC2 etc) on demand. As soon as the virtual machine image has been created you can download and use it
Skytap: You can create and run virtual test networks of a few or many servers on their grid
RightScale: Offers a nice cross-vendor interface for management of virtual machines in grids.
Kaavo: provides a simple and easy to use web interface to Cloud Computing (similar to rightscale)
Enomaly‘s Elastic Computing Platform (ECP) is a programmable virtual cloud computing infrastructure for small, medium and large businesses.
Scalr is a fully redundant, self-curing and self-scaling hosting environment utilizing Amazon’s EC2.