TInychat is a interesting yet simple service. It uses a ajax and does a pretty good job.

tinychat

It is pretty much like Chatterrous but bit simpler and could be used for a quicker light chat.

To create a chatroom, just go www.tinychat.com/chatroomname , replacing the chatroomname with the name you would like.

URL : http://www.tinychat.com/