How would you like to be able to have a WAS installation on your hardware without having to install WAS?
WebSphere Application Server Hypervisor Edition (press release) is the new edition of WAS that you install without having to install. The name is complicated sounding, but hypervisor simply means a program that runs in a virtual machine environment. WAS HV is WAS pre-installed in a VMware image. To "install" WAS HV, you simply copy the image onto a machine with VMware ESX or ESXi (or some other Open Virtualization Format (OVF) engine) installed, then use the engine run the image. The coping process makes "installation" much faster, easier, and practically full-proof.
When you install the image, you use one of several pre-configured profiles to make the server run as a stand-alone server, a cluster member, a deployment manager, etc. WAS runs in the image on, I believe, SUSE Linux; in the end, the OS WAS runs in doesn't matter as much as long as the VM engine supports it.
Other editions of WAS are base (aka stand alone), network deployment (ND), express, etc. Versions of WAS are v6.1, v7.0, etc. I believe both WAS 6.1 and WAS 7.0 are available as hypervisor editions.
Sounds like you deploy a Java EE application EAR to a WAS Hypervisor server the same way as a standard WAS server. This means you'll still need to resolve references to external resources (databases, etc.), which probably requires configuring the image to enable access.
See WebSphere charges into the clouds for a slicker marketing-sounding description. Note that while WAS HV can be installed via WebSphere CloudBurst, WAS HV can also be bought and installed without CloudBurst.
WebSphere Application Server Hypervisor Edition