I just sat and watched an awesome demo from google io on youtube link from the same guys/team that built the google maps application. For the last few years they have been working on google wave and boy is it going to be something special. It ticks all the right boxes as well for developers with some api skills - those with a vision for the way future applications need to operate, open-source and realtime will be able to do some wonderful things. With a new wave protocol to boot, google wave really is going to be something to get excited about.
You can find more information about google wave below.
http://www.waveprotocol.org
http://code.google.com/apis/wave
http://wave.google.com
