Google Wave is The Next Big Thing from Google
Google wave is currently in beta phase and only available to people who have received an invite. This then goes for the early-adopters and developers. On the internet there are inmidels quite a few people have been getting started, and not everyone is fully convinced of the power. Ultimately, it is a tool to work with and communicate with others. It's chat, it's office, it's wiki, it's email. And all brought together at 1 location (wave).
The good thing is that everyone can work on a wave at the same time, and you can see (rewind) later who did what. There is also an open API on Google wave so externals can also extend the platform.
What is Google Wave?
Google Wave Developer Preview at Google I/O 2009