This is neat. I can see this as the next 'wave' in virtual table top gaming. If someone had a tabletop they would be able to plug into Wave and get a whole lot of open source functionality.
Video presentation http://wave.google.com/
Articles about it http://blogs.computerworld.com/google_wave_who_what_where_why_when
http://www.techcrunch.com/2009/05/28/google-wave-drips-with-ambition-can-it-fulfill-googles-grand-web-vision/
http://googlesystem.blogspot.com/2009/05/google-wave.html
Sounds cool.