I'd like to personally welcome VMware to the cloud wars.
Today VMware announced its stand-alone ESXi hypervisor will be available at no cost. ESXi 3.5 update 2, available today, meets the criteria for mass cloud deployments: (1) ease of use and (2) maturity and stability now having been ‘battle tested’ for six months with customers. The leading server manufacturers have all embedded VMware ESXi, including Dell, Fujitsu-Siemens, HP, IBM, and NEC.
This is the first major step for VMware in the cloud computing scene. Historically VMware has focused on server consolidation and test / dev and has priced thier products accordingly. By making the underlying hyper visor free they effectivily enable cloud providers with the ability to utilize ESXi in their massive cloud server deployments while also helping keep their costs competitive with companies like Amazon who utilize Xen.
You can download ESXI from: http://www.vmware.com/products/esxi/