We are constantly editing environment variables in customer support and we know many of our customers access them frequently as well. Normally, you have to go through Start> Computer, right-click, select Properties, click Advanced system settings, click Environment Variables. Fortunately, you can cut about half that with a keyboard shortcut.
Windows Key + Pause/Break
Yes, it's that key way over on the upper right of your keyboard.
Hopefully you find this helpful. Free free to share your tips and tricks for quick access to frequently used windows or utilities.