I used ScreenLeap (http://www.screenleap.com/) to easily share my screen when I was having trouble with the projector. When you click “Share Your Screen” ScreenLeap will generate a code for you, along with a unique URL. Anyone on another computer/iPad will be able to visit the URL and see what you’re doing on your screen. You can pause or stop sharing at any time.
ScreenLeap would be a great way to quickly show someone how to do something on the computer, even if you’re not in the same room/building/state.