The 37 signals team has created an easy to use group chat service called Campfire. How does Campfire differ from Instant Messaging? In their own words:
Instant messaging is great for one-on-one chats, but it’s not optimized for group chats of 3 or more people. Further, instant messaging is network dependent — if you are on AIM, and your client is on MSN, you can’t instant message. Campfire, on the other hand, is all about simple and quick network-agnostic group chats. It’s a self-contained, password-protected web-based chatroom that allows groups of up to 40 people to chat and easily share files together. No instant messaging software is required — all that’s required is a web browser.
Update: 37 Signal founder answers questions about Campfire. His favorite answer to nearly any question? “It just doesn’t matter”
Nordquist Blog 