From the owners of VirtualBox, Sun Microsystems. Since taking over the VirtualBox application there has been great improvement in VirtualBox.
Here is list of OpenSolaris VirtualBox Virtual Disk Images. The OpenSolaris virtualbox images are should achieve the highest level of functionality with VirtualBox. One would expect the there will be feature "Only Available" to OpenSolaris Hosts and Client systems.
We will see how Sun and the developing VirtualBox community develop as time goes on.
