Copied from Sun xVM VirtualBox Homepage:


VirtualBox -- professional, flexible, open

VirtualBox is a general-purpose full virtualizer for x86 hardware. Targeted at server, desktop and embedded use, it is now the only professional-quality virtualization solution that is also Open Source Software. 

Some of the features of VirtualBox are: 


Modularity. 

VirtualBox has an extremely modular design with well-defined internal programming interfaces and a client/server design. This makes it easy to control it from several interfaces at once: for example, you can start a virtual machine in a typical virtual machine GUI and then control that machine from the command line, or possibly remotely. VirtualBox also comes with a full Software Development Kit: even though it is Open Source Software, you don't have to hack the source to write a new interface for VirtualBox. 

Virtual machine descriptions in XML. 

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

Guest Additions for Windows and Linux. 

VirtualBox has special software that can be installed inside Windows and Linux virtual machines to improve performance and make integration much more seamless. Among the features provided by these Guest Additions are mouse pointer integration and arbitrary screen solutions (e.g. by resizing the guest window). 

Shared folders. 

Like many other virtualization solutions, for easy data exchange between hosts and guests, VirtualBox allows for declaring certain host directories as "shared folders", which can then be accessed from within virtual machines. 

A number of extra features are available with the full VirtualBox release only: 


Virtual USB Controllers. 

VirtualBox implements a virtual USB controller and allows you to connect arbitrary USB devices to your virtual machines without having to install device specific drivers on the host. 

Remote Desktop Protocol. 

Unlike any other virtualization software, VirtualBox fully supports the standard Remote Desktop Protocol (RDP). A virtual machine can act as an RDP server, allowing you to "run" the virtual machine remotely on some thin client that merely displays the RDP data. 

USB over RDP. 

With this unique feature, a virtual machine that acts as an RDP server can still access arbitrary USB devices that are connected on the RDP client. This way, a powerful server machine can virtualize a lot of thin clients that merely need to display RDP data and have USB devices plugged in.


Changelog:


This is a maintenance release.
The following items were fixed and/or added:


Windows hosts: fixed host crashes/hangs on certain 32 bits Windows systems when running Linux guests (bugs #1606, #2269, #2763)

Windows hosts: Fixed network component BSOD issue (bugs #3168, #2916)

Windows hosts: Fixed installation issues (bugs #2517, #1730, #3130)


VMM: fixed performance regression for Windows guests (bug #3172)

VMM: ignore CPU stepping when restoring a saved state/snapshot


REM: fixed inability to use gdb to debug programs in Linux guests with software virtualization (bug #3245)


GUI: fixed dead key handling on Solaris hosts (bug #3256)

GUI: in the shutdown dialog, disable the action send the shutdown signal if the guest is currently not using ACPI

GUI: suppress additional key release events sent by X11 hosts when keys are auto-repeated (bug #1296)


API: restore case insensitive OS type name lookup (bug #3087)


VBoxHeadless: really don’t start X11 services (clipboard service, 3D acceleration; Solaris & Darwin hosts only; bug #3199)


NAT: fixed occasional crashes when the guest is doing traceroute (non-Windows hosts; bug #3200)

NAT: fixed crashes under high load (bug #3110)

NAT: fixed truncated downloads (Windows hosts only, bug #3257)

NAT: don’t intercept TFTP packages with a destination address different from the builtin TFTP server (bug #3112)


USB: several fixes for USB passthrough on Linux hosts

USB: reduced host CPU utilization if EHCI is active


VRDP: fixed VRDP server black screen after a client reconnect (bug #1989)

VRDP: modified rdesktop client (rdesktop-vrdp) now uses NumLock state synchronization (bug #3253)


LsiLogic: make FreeBSD guests work (bug #3174)


ATA: fixed deadlock when pausing VM due to problems with the virtual disk (e.g. disk full, iSCSI target unavailable)


iSCSI: fixed possible crash when pausing the VM


3D support: added missing GL_MAX_TEXTURE_COORDS_ARB (bug #3246)


Windows Additions: fixed ERROR (e0000101) error during installation (bug #1923)

Windows Additions: fixed Windows Explorer hang when browsing shared folders with 64 bit guests (bug #2225)

Windows Additions: fixed guest screen distortions during a video mode change

Windows Additions: fixed the Network drive not connected message for mapped shared folders drives after the guest startup (bug #3157)


Linux Additions: fixed occasional file corruption when writing files in O_APPEND mode to a shared folder (bug #2844)

Linux Additions: the mouse driver was not properly set up on X.Org release candidates (bug #3212)

Linux Additions: fixed installer to work with openSUSE 11.1 (bug #3213)

Linux Additions: disable dynamic resizing if the X server is configured for fixed resolutions

Linux/Solaris Additions: handle virtual resolutions properly which are larger than the actual guest resolution (bug #3096)