rpath have created a new open source openstack cloud appliance to help simplify OpenStack deployment and upgrade for organizations building their own private clouds
VMware vCloud Express is an Infrastructure as a Service (IaaS) offering delivered by leading VMware service provider partners. It is a co-branded services that provides reliable, on-demand, pay-as-you-go infrastructure.
According to VMware VMware Workstation 8 is your on-ramp to the cloud. With over fifty new features, it’s going to dramatically change the way you work with virtual machines.
Oracle are now saying that their VM is “4x cheaper and 4x more scalable” than VMware and have created a page where you can calculate how much you will save by switching to Oracle VM.
http://cloud-computing.findthebest.com/opsource have created a useful cloud comparison page comparing the amazon ec2, gogrid, opsource and rackspace clouds
or use find the best to create your own cloud grid comparison chart