I realized recently that the different products in the Sun xVM portfolio might start to blend together after a while. I mean, they're meant to work together, but we haven't talked about what features are stand-alone and what aren't. So I'll start by talking about what Sun xVM Server does - by itself, and in combination with Sun xVM Ops Center.
Sun xVM Server is an x86/x64 hypervisor based on OpenSolaris and the work of the Xen community. It's Type 1, so it's installed on bare metal, and it includes the framework for managing guests (our term for virtual machines) and a web server which produces the browser user interface (BUI).
Once Sun xVM Server is available (soon), you'll be able to download and install it. Getting it up and running takes us an hour, but that could vary based on your hardware. Once it's up and running, you have several options for guests - Windows, Solaris, OpenSolaris, and Red Hat. It can also import existing VMware appliances. It supports both hardware-assisted virtualization and paravirtualization, and can generally handle as many active guests as you've got memory and space for. You can manage the Sun xVM Server and all of its guests from any browser through the BUI.
If your environment is larger scale, then Sun xVM Ops Center - our datacenter management tool - can be used with Sun xVM Server. You can use Sun xVM Ops Center to combine multiple Sun xVM Servers into Virtual Pools, which let you migrate guests between Sun xVM Servers. Virtual Pools can also be set to automatically load-balance your Sun xVM Servers or move guests to another system in the case of a hardware failure.
That's the short version, at least. There's a video demo that may be helpful as well. If you have any Sun xVM Server questions, ask away. I'll follow up with similar explanations of the other products in the portfolio.
Edit: If you're interested in getting your hands on Sun xVM Server as soon as possible, you can sign up for early access by sending an email to firstname.lastname@example.org. They'll add you to the list and hook you up with an ISO.