Any Mac and Linux users out there are likely familiar with the concept of having multiple virtual-desktops. On the Mac it is referred to as Spaces. Basically, it lets you use your computer and then hide everything and have a whole screen off to the side that you can switch to with different tasks going on.
I'm an avid multi-desktop user. I use it mostly to separate "work" from play. I have web browsing and IM on one desktop, the next will have my iTunes open or something, the next will have some files I'm playing around with, and often the last will have my code open for some project I'm procrastinating. It's great since it allows me to leave things the way they were and switch flows entirely without disrupting my progress in what I was doing.
One modern operating system that is sorely lacking in a native implementation is Windows 7. For some reason Microsoft has yet to incorperate this feature. While looking for a good and lightweight option for Windows I found mDesktop. It's very small and gets the job done. When I found it it was very no-frills. Basically what I was looking for. To my excitement I found that it was also Open Source!
I started asking questions and taught myself AutoHotkey scripting so that I could start implementing some of my ideas. After my request to share what I had done, the project creator has let me join the "team". It's a free piece of software that I am excited to keep working on.
If you used a Mac or Linux computer and have been dying for a program to do the same on Windows, then this will get the job done. If you're someone who's never even knew this kind of thing existed, then download it and give it a try! It's free! If you have any questions about it, you can ask here or on the projects page under Issues or on the Wiki. http://code.google.com/p/mdesktop/