Virtualbox in my opinion is the best virtualization software. I have tried other software like VMware workstation it was nice but I always came back to virtualbox. Something about it just always bring me back to it. Its easy to use runs just about anything. Can create virtual networks or just run vm to test out software.
Oracle VM VirtualBox is an x86 virtualization software package, originally created by software company innotek GmbH, purchased by Sun Microsystems, and now developed by Oracle Corporation as part of its family of virtualization products. It is installed on an existing host operating system; within this application, additional guest operating systems, each known as a Guest OS, can be loaded and run, each with its own virtual environment.
Virtualbox will run just about anything including Windows, Linux, Mac, FreeBSD and many more. I run mostly Windows and linux machines on my virtualbox installation. It can run multiple vms at a time, but the things that can limit the number of machines ran at once is memory and cpu speed. My computer has a intel core i3 m 370 and 4gb of memory. It can run 3 to 4 vm at a time. If I would add more memory it could run more.
Supported host operating systems include Linux, Mac OS X, Windows XP, Windows Vista, Windows 7, Solaris, and OpenSolaris; there is also a port to FreeBSD (only OSE version). Supported guest operating systems include versions and derivations of Windows, Linux, BSD, OS/2,Solaris and others. Since release 3.2.0, VirtualBox also allows limited virtualization of Mac OS X guests on Apple hardware.
If your a Developer oracle has created some pre-built vm for you to download and install and use to develop with you can find those downloads here.
You can find more information over at virtuabox’s website.