VirtualBox is one of the opensource survivors from when Sun was acquired by Oracle. It is one very useful tool. Oracle's VirtualBox 4.1 includes several new features, but the main one is a new virtual machine cloning facility, which adds a lot more functionality to keep up with a growing sector of VDI competitors.
The other features of this major release are enumerated in the changelog.
- Support for cloning of VMs (bug #5853, see the manual for more information): full clones can be created through the GUI and VBoxManage, linked clones only through VBoxManage
- GUI: enhanced wizard for creating new virtual disks
- GUI: new wizard for copying virtual disks
- GUI: keep the aspect ratio in scale mode (Windows and OSX hosts only; bug #7822)
- VMM: raised the memory limit for 64-bit hosts to 1TB
- Experimental support for PCI passthrough for Linux hosts, see the manual for more information
- Windows guests: Experimental WDDM graphics driver, supporting Windows Aero (bug #4607) and providing Direct3D support using a cleaner approach (no need to install the guest drivers in Safe Mode anymore)
- Guest Additions: status of modules and features can now be queried separately by the frontends
- Networking: new network attachment mode "Generic Driver", which offers an open plugin architecture for arbitrary and separately distributable virtual network implementations
- Host-only Networking: fixed host crash in kernels prior to 2.6.29
- New Networking Mode UDP Tunnel: allows to interconnect VMs running on different hosts easily and transparently, see the manual for more information
- Experimental support for SATA hard disk hotplugging available with VBoxManage
- Solaris hosts: New Crossbow based bridged networking driver for Solaris 11 build 159 and above
Download from the usual place.