SlideShare has launched a new service called Zipcast with buttons on every public slideshow that turns the slides into a Webcast with video, audio and chat.
And to share the slideshow meeting, all you have to do is pass out a regular link—every SlideShare user will get a customized link that looks something like http://www.slideshare.net/erick/meeting and that can be used over and over again for every meeting that person hosts. Participants can sign in with Facebook and can choose to send their chat comments out to their Facebook streams, along with a link back to the meeting, which is a good way to gather an audience for live events. Zipcast will have its own page with an activity stream showing what meetings are going on right now , along with comments, which could also drive more people into public meetings.
There is no limit to how many people can join a meeting, Meetings can be public or private, but anyone with the link can view the presentation.