First, you need VMWARE Workstation installed on at least one machine. I have it on my laptop. To just play the machines you need VMWARE player which is free from VMWARE.
Sandbox BrowsingOne way that I have been using virtual machines is what I like to call a sandbox Internet machine. I created a Ubuntu Virtual Machine and installed the VMWARE tools. Once I got it working, I set it up so it can network between itself and my host machines which are often Windows XP or Windows 7. At work, I do not want any browsing to inadvertently pick up any virus or spy-ware. So I use VMWARE player to play my Ubuntu machine. I use it just like any application, but with Firefox in Ubuntu I find a very safe browsing machine. I can still download and transfer files between my Ubuntu machine and the host. Also cut and paste works pretty good between the Virtual machine and any host application that I have working. I use Dropbox to open and save files across all my machines (see next below) I like this setup so well, that I am thinking of possibly use it in every environment. [note: here is a pre-built Ubuntu appliance although it is version 8 so you don't even have to create it]
Single Application MachineAnother way is like I mentioned above, but this time my Virtual Machine is Windows XP. After I created it and put on all updates. I stripped down the services to bare minimum to make start-up and shutdown as fast as possible. I set the wallpaper and interface to maximum performance. Then I made sure that OneNote was working perfectly. I put this VM on a portable Hard Drive. Now I have my OneNote application in whatever machine I am on. This is important to me because I do not have OneNote available to me on my work machines, but with VMWARE player, I just plug my portable drive in play the machine. Now I do something else that I also do on my Ubuntu machine, I use Dropbox (Dropbox is cross platform. You can install it on Windows, Linux and Macs). With Dropbox, I keep my Notebooks in Dropbox which allows me to open my Notebooks with OneNote in any other machine that I have OneNote installed.
A Teaching EnvironmentA third way is actually a bunch of other ways. I also teach some Technical classes and I find VMWARE Workstation indispensable in that role. I every operating system I can installed in VM Workstation along with routers and Virtual Storage devices.
A Test and Development EnvironmentThis is probably not needed to be mentioned, but this is the most efficient way to test and develop applications and set up test environments. You can isolate whole systems within your own PC/Laptop. I can easily create a whole Lan/Wan simulation and test real time environments. Test environments like these use to take me a great deal of time, numerous pieces of equipment and not to mention dollars. Not only that but the test environment was unmovable. With a Virtual Environment my test lab travels wherever I go. Again, I just could not work without it.
I really do not know how I use to work without Virtual Machine technology, but without it, I would be lost.