Open Source & Node.js-Powered Chat App: Balloons.IO
Balloons.IO is a very impressive and open source chat application that is built with node.js, Express, Socket.IO and Redis.
It has support for multiple rooms where users can join any of them, chat with other users and send files to each other.
Also, there is an option for users to create their own rooms and set their statuses (available, away, busy)
The application is simple-yet-solid and requires users to login with their Twitter accounts (which is good to keep the quality "up" but can be limiting). It also automatically fetches the avatar and uses is with every message of each user.
Compatibility: All Major Browsers