The Access Grid is a massive audio and video teleconferencing project run by and participated in by a large number of educational and research institutions around the world.
By using multicast over Internet2, the video conferencing tool vic and the audio conferencing tool rat, along with various custom software to tie it all together, the Access Grid creates virtual rooms. Groups of people all over the world can collaborate with each other as if they were in the same room.
Each physical location participating in the grid generally has a presenter camera, an audience camera, and a main camera, as well as various microphones and an echo canceller, usually a Gentner AP400. Video feeds from other locations in the grid are displayed at the front of the room using one or more multimedia projectors.
The Access Grid is currently one of the largest utilizers of Internet2 bandwidth. It shows what is possible when you have multicast and ridiculous amounts of bandwidth.