Google Wave was introduced at Google IO 2009. I think its game over for Microsoft :). Wave is a new browser based tool for communication and collaboration on the web, coming later this year. You have to watch the video to get the full WOW.
Google Wave is what email would look like if it were created today. One feature i have to mention is the ability to imbed a wave into a webpage. The demo video shows how this is used to create a blog with it. It starts around the 20:20 minute mark.