If you are running on top of your dedicated servers, the providers are now all providing a dedicated VLAN for your servers. This allows you to deploy your own VM management software on top of your dedicated servers.
If you can, I recommend you to use Ganeti with Xen or KVM (I use KVM). Rigorous development, very friendly developers and very well designed tools. No wonder it is used internally at Google.
Yes, but, it would be a dead horse, they would have not been keeping it in production and improving it over the past 5 years. I think this is the key, well designed, well maintained, well used for critical stuff in a big company all that over several years.
If you can, I recommend you to use Ganeti with Xen or KVM (I use KVM). Rigorous development, very friendly developers and very well designed tools. No wonder it is used internally at Google.
http://code.google.com/p/ganeti/ - Project page.
http://notes.ceondo.com/ganeti/ - Notes on how to use it with Debian (long).