VirtualBox is a full virtualizer for x86 hardware. The software will allow you run virtual environments within your current set-up.  You can run Mac, Windows or Linux operating systems within VirtualBox.  The software is now the only professional-quality virtualization solution that is also Open Source.

Key Features Of VirtualBox:

VirtualBox has a modular design and well-defined internal programming interfaces.  The design makes it easy to control it from several interfaces simultaneously.  For instance, you can start a virtual machine in a typical GUI and then control that machine from the command line interface.

With VirtualBox you can have multiple virtual machines.

With VirtualBox you can have multiple virtual machines.

The configuration settings of virtual machines are stored entirely in XML and are independent of the local machines.  Subsequently, Virtual machine definitions can easily be ported to other computers.

The following changes of additions or fixes have been made in this version of VirtualBox:
VMM: more fixes for MSR emulation on certain hardware
VMM: improve MSI handling under rare circumstances (only relevant for the ICH9 chipset)
VMM: fixed #UD exception for 64-bit guests with the EFER.SCE bit and the SYSCALL instruction (VT-x only; 4.3 regression)
VMM: fixed timekeeping after resuming a multi-CPU VM
GUI: fixed a potential crash
GUI: fixed stuck AltGr key on Windows hosts
GUI: fixed a potential error during the version check
GUI: shortcut change should not require Enter/Return (or other trigger) to confirm
NAT: fixed inbound half-close
NAT: fixed slow upload speed under certain conditions
NAT Network: fixed inbound half-close on Mac OS X hosts
NAT Network: fixed socket leak on Solaris hosts
NAT Network: fixed ping of mapped host loopback on Mac OS X and Solaris hosts, fixed proxying of IMCP errors on Mac OS X
Host-Only Network: fixed SNMP ifConnectorPresent value on Windows
Storage: fixed a possible crash with CD/DVD pass-through under certain circumstances
Storage: fixed a crash when trying to open an inaccessible QED or QCOW image
Storage: fixed data corruption or read errors under rare circumstances
AHCI: fixed a crash under rare circumstances
USB: performance fixes
ICH9: properly reset MSI capability on reset
3D: fixed misbehaviour with huge guests (i.e. guest more than 4GB guest memory
3D: several fixes
API: properly detect the Windows 8.1 guest OS type
Linux hosts / guests: compile fix for EL7
Linux Additions: made 3D pass-through work with recent versions of Mesa in the guest
Mac OS X hosts: when scanning for host CD/DVD devices also consider Blu-Ray devices
OS/2 Additions: fixed gengradd.dll library name
Solaris Additions: fixed permissions of files and directories located on shared folders

You can download the latest version of VirtualBox from today.

[Image via geekoversity]