ArrowChat is a Facebook style chat plugin.
Similar to Wibiya, the Meebo toolbar and CometChat, Arrowchat functions independently from WordPress, which means that the user must install it.
This plugin makes installation much easier and more streamlined by circumventing the process of having to modify theme files.
Arrowchat is a premium service, find out more at: www.arrowchat.com
Download plugin: http://wordpress.org/extend/plugins/arrowchat-wordpress-integration/