This is an amazing new app from Google that allows instant texting, email combined with live/real time bulletin board, and shared pictures á la Flickr. But that's not all--you can blog and embed the pictures and continue the conversation live via the blog or social network, e.g., on Orkut. Anyone can join in at any point in the conversation, and get a playback of what went on before--or create a private "thread" on the side with specific users. Best of all (for some) it is open source, so you can make your own applets for it.
Or catch the Google Wave preview here.