Microsoft Server Next Gen Virtualization for Free
Microsoft Hyper-V Server 2008 R2 is a free release of Hyper-V server. It does not contain a GUI, but free remote management tools are readily available. The new R2 release contains features previously only found in the higher priced Windows Server 2008 R2. These features include Live Migration, 8 physical processor support, 24 processor cores, 1 TB of RAM, and up to 384 running virtual machines (now that would be a heck of a host server!). You can read more about it at the Windows Supersite and download your free copy at Microsoft. Stay tuned for more on virtualization and Hyper-V.