This tutorial provides step-by-step instructions on how to install VMware Server (version 1.0.6) on an Ubuntu 8.04 desktop system. With VMware Server you can create and run guest operating systems ("virtual machines") such as Linux, Windows, FreeBSD, etc. under a host operating system. This has the benefit that you can run multiple operating systems on the same hardware which saves a lot of money, and you can move virtual machines from one VMware Server to the next one (or to a system that has the VMware Player which is also free).

http://www.howtoforge.com/installing-vmware-server-on-ubuntu-8.04