Wow...just used the https://join.me/ for the first time. I called a support person who directed me to go the the join.me page and just click Share and then Basic. 30 Seconds later I told her the 9 digit number that popped up and voila she could see my screen and talk me through the steps needed. So Simple, Easy and Free.
So...To share your screen, simply download a small app, and then send the 9-digit code generated to your potential collaborator. They either click a link in the email, or go to the join.me website and input the code, and they can see your screen.
It fills a different need than the typical scheduled web conferencing solution (ie. GoToMeeting, WebEx etc). It is for instant web conferencing...click...click...read off a 9 digit number...they can see your screen. Try it...you just might be as impressed as I was.