Google Wave

Google is previewing a new web application to developers that may eventually supplant Gmail. Google Wave goes beyond the basic capabilities of email in order to let people communicate and work collaboratively in real-time with text, photos, videos, maps, gadgets, and social networking feeds from other sources on the internet.

A "wave" is equal parts conversation and document. A user starts off by creating a wave and adding people to it. Everyone on a wave can insert a reply or edit the wave directly. It is being billed as concurrent, collaborative rich text editing, where you can see on your screen nearly instantly what your fellow collaborators are typing in your wave. That means Google Wave is well suited for quick messages as well as for persistent content. A "playback" function is also available to rewind the wave and see how it evolved.