EchoWaves - Opensource Social Group Chat written in Ruby On Rails
JabbR - A chat application built with ASP.NET and SignalR.
Shtuff Chat - Free Group / Team chat with persistent history.
Worlize - Worlize is the platform that allows users to communicate with each other in a fun way and play games that are created by the users on this platform.
Anologue - Disposable online chat.
Chattp - Chattp is the software that simply converts your page into chat by augmenting the browser Windows.