It is not any where near perfect yet, but meebo.com is interesting. It is AJAX, it is Instant messaging, and it seems to support the major clients.

I tried it out, and it was not perfect. I had one window for me sending information and one window to recieve it…for the same conversation. It is a thrilling idea though. Soon we will not need any applications on our computer. Just our data, and a connection to the Internet. Exciting times.