Those sites offer chat scripts that have an HTML output on the client side (for the end user). Many of those scripts are free. Those also tend to be useable by such systems as WebTv, but this depends on the script itself.
All sites submitted to this Category must have a HTML output. Those could include Perl Scripts (*.pl and *.cgi files), PHP (all versons), severlets/JSP, and ASP. Working demos of the room are a plus, as is the ability to install the scripts via FTP.