Free virtualization with VMware vSphere
The free vSphere Hypervisor 5.0 lets companies enter into professional virtualization without the overhead of a commercial solution. If you decide you need additional enhancements later, you can always upgrade to enhanced VMware solutions.
Competition in the commercial virtualization market has become very fierce, but the market leader, VMware, also offers a virtualization solution for free. vSphere Hypervisor 5.0 is the successor to the likewise-free ESXi server. vSphere offers all the critical functionality an administrator needs for getting started with virtualization, and if you are looking for more advanced features, like high availability or better data backup for virtual servers, you can upgrade to commercial VMware variants without the need to reinstall.