Sadly, today Google announced that Google Wave is dead.
Writing in the Google Blog, Urs Hölzle, Senior Vice President, Operations & Google Fellow, stated the following: "Wave has not seen the user adoption we would have liked. We don’t plan to continue developing Wave as a standalone product, but we will maintain the site at least through the end of the year and extend the technology for use in other Google projects."
You can read more in the Google Blog at http://googleblog.blogspot.com/2010/08/update-on-google-wave.html
You can read my earlier articles about Google Wave at http://blog.eogn.com/.services/blog/6a00d8341c767353ef00e55065e13d8833/search?filter.q=google+wave