Wave is an amazing demonstration of where the web is going, and our lives are going to be richer for it. It's an entirely new approach to personal communication, and clearly demonstrates that open architectures are (pun intended) the wave of the future. Google are actively looking for people to get involved with the project already.
More later. For now I am too blown away to do much more than sit here thinking about the potential. I am also excited that this represents a bundle of opportunities for the open source world to demonstrate technical leadership. Unless other vendors have come up with some competing web-based technology I'm not aware of, and I'd be happy to learn about that too.
Information about the Wave platform (and, of course, the open source code) is on Google Code. The open Wave protocol details are on a separate site. Look for Wave's public arrival later in the year. Nice job, Google.