The free virtualization platform Hyper-V Server 2008 R2 is now available to download.
MS stand-alone free product has nice improvements regarding to V1 of the same product. Hyper-V Server 2008 R2 allows Live Migration, Hot add/remove virtual storage, support for 64 logical processors, support for running up to 384 virtual machines with up to 512 virtual processors, live migration across different processor SKU’s from the same vendor, Networking enhancements, Boot from flash, etc...
Try it at:
Microsoft® Hyper-V™ Server 2008 R2
Comparing Hyper-V Server V1 vs. V2