I have used this before, but reinstalled windoze and Skype, so I lost it. I only reinstalled it again recently and was amazed to see what good of a FREE product this really is:
Basically, this is WebEx for a small audience - you share your desktop, invite others to take control of your desktop, do white-boards and because it's all integrated with Skype, you have voice call and chat.
The free version limits you to 11 people to share the desktop with, but I hardly ever need more. The paid version comes without this restirction.
The installation was a bit cumbersome: Go to any person in your Skype list, click on menu (little grey box), 'do more...', 'get extras' and search for it. You start to download it, then it takes ages to install. You must afterwards create a new account (yes, it doesn't tie in all the way in). When you get an alarm asking you if you want to allow Java to do stuff, say 'yes' and it should be good to go.
To start, you now have to click on 'menu' -> 'do more' -> 'organise extras' and you should have a link in there.
There is also a desktop / Skype independent version of this handy tool. However, I use it with Skype and was never interested in having it install as a seperate programme.
Have more fun and be more productive with sharing!