Google Wave is a real-time communication platform. It combines aspects of email, instant messaging, wikis, web chat, social networking, and project management to build one elegant, in-browser communication client. You can bring a group of friends or business partners together to discuss how your day has been or share files.
Google Wave has a lot of innovative features, including Real-time typing, Blog or Website Embeddability, Applications and Extensions, (just like Facebook), Wiki functionality, Open source, Playback, Natural autocorrection of spelling, and Drag-and-drop file sharing.
You've got to have it!