So this is my current desk setup. There are four computers; my MacBook pro is the day to day workhorse for email and design work. Then there are two dell Vostro 200's. One runs Vista and Vista 64 in a dual boot configuration for testing and development. The Second Vostro is running Server 203 for testing enterprise options and running a print server. the fourth machine is a legacy business desktop for testing performance on older hardware.
The whole set up is controlled via a single mouse and keyboard using the virtual keyboard and mouse software Synergy. This allows me to scroll to the edge of the monitor of my mac and then be in control of the machine to the right of it. It is not always totally seamless and to get it to work smoothly on Vista it needs to be run as an administrative user and disable the godawful UAC.