Just a few weeks ago, Sun had introduced xVM – a family of virtualization solutions based on the technology of open source project called Xen.

Recent builds of OpenSolaris have full support for xVM, which means that you can activate it by booting Solaris in a special mode (it's a separate menu item in your Grub boot loader menu).

As always, Sun not only invests a lot of time into development of the project, but all the findings are open-sourced, and there's a hub for related projects: OpenXVM.