My manager just mentioned this feature of PowerPoint 2010, and it seems cool enough to share / remember. So, check out this blog post from the PowerPoint Team Blog, titled Introducing Broadcast Slide Show. There’s a video to show this nice little feature. They say:
PowerPoint 2010 makes it easy to present on the fly to anyone, anywhere. Just send a link, and in one click everyone you invite will be watching a synchronized view of your slide show in their browser. You’ll never again need to email bulky attachments or make an announcement every time you change slides.