Today, I was watching a software demo and saw a cool thing. The guy was demonstrating how various people would interact with his company's software, and he brought up a 3D cube on the screen with a different user's desktop and browser on each side of the cube! It was awesome, so I asked him how he did it right after the demo.
He was using a utility called "DeskSpace" to make it happen. I downloaded a trial copy and recorded a short demo video of DeskSpace so you can see how it works, below (note that the video is choppy, but that is a symptom of the refresh rate on the capture - in real life, this is very smooth and "slick" in appearance).
This is a Windows app and seems to be fairly stable (I'm running it on Vista, but it also works on XP). Each desktop looks like a different system, since the status bar for an app only appears on the desktop where that app is running. This doesn't change the performance of your system since you're really just running the apps inside one instance of an OS, but it does make it easy to create an uncluttered collection of desktops.
For example, I experimented with Outlook on one desktop and a couple of browser sessions, each on a different side of the cube. It was cool to be able to switch around. I can see this being handy if you have a "context switching" kind of job - such as one pane for a CRM, one pane for email, one pane for web research, etc.
There is a free trial if you want to dabble, and it's $20 to buy. I'm still demo-ing for now.