I used my GSTAR-EX camera and Skype to give a series of night sky tours to a hall of people from a UK club a couple of years back. It worked very well indeed and gives probably the best results for limited bandwidth ie std adsl.
If you fancy broadcasting to a wider audience, then
www.ustream.tv has a very good service. Search on astrojunk to see some of my broadcasts last year. The downside is the need for plenty of bandwidth to get decent quality.
There is plenty of software available to turn just about anything into a virtual webcam - it's just up to your imagination as to what you want to show.
Have a go, it's loads of fun to skype a mate and show them something out of this world!!