Open Source Virtualization Software
Sun VirtualBox, is an enterprise-class open source software that runs on all major operating systems.
Sun VirtualBox is a small-footprint, high-performance, virtualization platform that installs and runs just like an application on your existing Windows, Solaris OS, OpenSolaris, Mac OS X, or Linux “host” OS. It lets you create multiple virtual machines into which you can install whatever “guest” OS you need. So the same computer can run multiple operating systems and applications at the same time.
The new version is very useful for packagers as it provides multiple snapshots and it is free!!.
Read more about the FAQ using the below link