VirtualBox is a powerful x86 and AMD64/Intel64 virtualization product for enterprise as well as home use. Recently, VirtualBox 4.1.4 has been released and is ready for Ubuntu 11.04. This release has come up with basically bugfixes only as it is a maintenance release. So, no goodies for anyone, atleast for now. But many annoying bugs like memory leak, GUI bugs while running KDE, add support for X.Org Server 1.11, fixed compiz bugs and numerous others. For details regarding the bugfixes please see the changelog.
Simple download the file and open it with Ubuntu Software center and it will install your Virtual box and start your OS testing lab :P.