PowerPoint 2010 users can access the PowerPoint Broadcast Service using a Windows Live ID. When you start a broadcast, it’ll provide a public link that you can send to anyone on the Internet you invite to present your slide show with people in different locations on the fly. Just open any presentation in PowerPoint, click Broadcast Slide Show, and connect to the PowerPoint Broadcast Service. You’ll receive a unique link that you can email or IM to remote attendees. Then, start the slide show and present the same way you do for every presentation you give with PowerPoint.

Source:→ PowerPoint blog