I use VM's quite often so I got to thinking there must be some kind of specialised solution for running VM's on a thinner and lighter GUI based host shell then a general user OS. But as it turns out there isn't actually a ready made desktop solution as such. But if you've got a spare blade/server class machine lying about somewhere you might want to give VMware's ESXi 5 vsphere hypervisor a go. It's essentially a fully featured  industry class bare metal host machine server OS specifically designed for virtualisation. It's also free to download and use, however the catch is that it doesn't come with technical support of the immediately contactable staffed kind despite having a full in depth set of documentation to help you trouble shoot any potential issues that you might encounter whilst using it. I kind of switched off when I saw the hardware requirement's since it was essentially all of the dedicated server variety which would have left me a little stuffed trying to get direct hardware access for my VM's with a general lack of hardware support for my rather paltry system specs in dedicated server system terms, i.e. I don't have access to the kinds of server class hardware needed to run it. (...although theoretically it should be infinitely thinner and lighter then running VMware workstation 8 over Windows 7 or VMware fusion over OSX). 

They also have another premium ESXi variant (as in the version you have to pay for) that does come with full technical support along with a few additional features. However you'll find that the free version pretty much has nearly all the premium grade features besides one or two so its ideal for testing and educational purposes (not to mention that its potentially fully deployable for full use in a practical scenario in competent hands).

You can go directly there and grab the download there by clicking here.