Quick Screen Share is a free screen sharing service from the makers of Screencast-o-matic. To use Quick Screen Cast just go to their website, select share your screen, and enter your name. Quick Screen Share will then provide you with a URL to share with the person with whom you are screen sharing. When that person opens the link you he or she will be able to see your screen.
Quick Screen Share doesn't require you to install anything (assuming you have Java installed) or require you to register for the service.
Applications for Education
If you provide online support to your students, Quick Screen Share could be a very handy tool when typed or spoken words alone do not provide enough clarity.