Howtoforge posted a new tutorial about installing VirtualBox on Ubuntu

This tutorial shows how you can install InnoTek's VirtualBox on a Ubuntu desktop. With VirtualBox you can create and run guest operating systems (virtual machines) such as Linux and Windows under a host operating system. There are two ways of installing VirtualBox: from precompiled binaries that are available for some distributions and come under the PUEL license, and from the sources that are released under the GPL. This article will show both ways.

Installing VirtualBox On Ubuntu