This particular link, http://nikpeachey.blogspot.com/2008/01/make-your-own-chat-room.html, takes you to an excellent overview of how chat rooms can be used with learners by setting them goals and tasks, as well as pointing you towards on-line software that allows you to set up your own chat room.

Or you can just go and browse the whole blog at http://nikpeachey.blogspot.com/.