This is a genius idea. ThemeFlash.com has a great list of 45 cheat sheet wallpapers for web designers and developers. Some of my favorites so far include the Photoshop shortcuts, Periodic Table of Typefaces, and The Anatomy of Type. I'd love to see some Visual Studio or Windows 7 shortcut wallpapers. Remember, if you're working in an application and you want to see the list of shortcuts, all you need to do is drag your mouse down to the bottom right 'show desktop' area, or hit Windows+Space Bar on your keyboard.