VirtualBox is a powerful x86 virtualization product for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers, it is also the only professional solution that is freely available as Open Source Software under the terms of the GNU General Public License (GPL).
Presently, VirtualBox runs on Windows, Linux, Macintosh and OpenSolaris hosts and supports a large number of guest operating systems including but not limited to Windows (NT 4.0, 2000, XP, Server 2003, Vista, Windows 7), DOS/Windows 3.x, Linux (2.4 and 2.6), Solaris and OpenSolaris, and OpenBSD.
- 64-bit guests (64 bit hosts with CPU virtualisation extensions or experimentally on 64bit capable 32bit host operating systems)
- NCQ support for SATA raw disks and partitions
- Seamless mode
- Shared folders
- Special drivers and utilities to facilitate switching between systems
- Experimental OpenGL drivers for win32 and Linux to render on Host hardware
- Command line interaction (in addition to the GUI)
- Public API (Java, Python, SOAP, XPCOM) to control VM configuration and execution 
- Remote display (useful for headless host machines)
- Nested paging for AMD-V and Intel Core i7
- Raw hard disk access - allows a guest operating system to access its virtual hard disk without going through the host OS file system
- VMware Virtual Machine Disk Format (VMDK) support - allows VirtualBox to use a disk image created in VMware
- Microsoft VHD support