We've recently built a system(web application) where you can create a chatroom and embed it on your website, in a simple manner, all free. It requires no plugins to run(no flash/java).
The website is located at www.e-chat.co so please have a look and give us feedback.
If you have any queries or would like to drop us feedback, send message to firstname.lastname@example.org
Cheers, E-Chat team.