Google Wave

Google Wave is an alternative to e-mail, instant messaging and file-sharing sites—and combines the best of each in one place. Your inbox shows a list of “waves,” or savable, enhanced online conversations. Pals and co-workers invited to a wave can chat in real time, drag and drop images and documents, and edit past contributions, making it an ideal collaboration tool. And because Wave is open to developers, its capabilities will only grow. For instance, people can create apps that automatically insert news clips into waves or gather polling data from your contacts.
wave.google.com