Alot of people are using Skype. Its a very popular tool. I just found out about a new FREE tool that allows you to do webinars via skype. It's called Yugma. You share your desktop with 10 attendees for free. Now for a few bucks a month you can also share mouse and keyboard control with attendees, schedule sessions, record sessions, webinars, change presenters, and use the "white board" tool. The more attendees you add the more your monthly fees will be. It looks very interested. I plan on trying this in a future "live training" session at the School of Podcasting to see how it compares to some of the other tools I've used. I really like the free feature, and the fact that I can run it on any computer (and yes its cross platform for you mac people),
You can try all of these features forfree for 15 days. If you have a group of 10 or less you can have all the premium features for 10 bucks a month. If you have between 10-20 attendees its only $19.99 a month.