Virtualization is the next big thing in computing. I've been using VMware, Qemu, MS Virtual PC and a couple others for years, so it is obvious that virtualization isn't new. I regularly work on OpenVZ environments where we run dozens of servers in one physical box, and in some cases we've been able to reduce entire datacenters to a single blade center. That is amazing. Recently virtualization has gotten a lot of attention and finally seems to be coming to maturity and mass adoption. Even Oracle has jumped on the bandwagon. Their product, OVM is awesome.
Oracle VM Manager is based on RedHat and it allows you to have a pool of resources to configure, deploy and manage virtual machines in your enterprise. Unfortunately you have to pay a subscription fee to get some of the important things, like official yum repositories, but if you have the hax0r skills you can create your own repos and use those instead. Take a look at a couple of the screenshots.
For a highly technical overview of features, you could take a look at their official wiki page. http://wiki.oracle.com/page/Oracle+VM+Features