Campfire is a web-based group chat tool from 37signals. It's like Instant Messaging, only better because it's designed for groups and runs in your web browser.
Conducting group chats in a web browser is a huge win, and Campfire™ is an exceptional example of a full-featured application that runs in an ordinary browser.
But if you use Campfire™ for hours every day, a web browser simply can't deliver the desktop-grade experience you expect from an application that's "always on".
With a clean interface, smart drag-and-drop, custom notifications and more, Propane makes Campfire™ a joy to use on Mac OS 10.5. Check out the screencast or better yet, download it and see for yourself.