ChatJS is a full-featured, lightweight, Facebook style jQuery plugin for instant messaging. ChatJS also comes with a server side implementation for ASP.NET/SignalR out of the box.
Features:
Real time message sharing.
Automatically parses URLs and emoticons.
Automatically remembers opened windows across diferent requests (through cookies).
Triggers a sound notification when the user receives a message.
Indicates when the other user is typing.
Supports multiple chat rooms. If you have a multi-tenancy app you can create a room for each tenancy, for instance.
Supports multiple browser windows opened with the same session. They all get properly sinchronized.
Customizable texts. You can easily translate it to your language.