Yahoo Zync, watch videos with your friends in sync
Yahoo kicked off this project at Yahoo Research Berkeley, a facility to explore and invent social media and mobile media technologies. The Zync plug-in allows video sharing in sync and in real time. Instead of sending friends an IM with the video link, videos from YouTube, Google videos, and of course Yahoo, can be played in the browser between friends in sync. Both parties also have control of the playback of the video, and chat about it instantly.
The Zync plug-in is currently only available for PC's.