Parleremo uses AJAX Chat for people to talk with. No software is required to use it, but Javascript is required.
AJAX Chat is a free and fully customizable open source web chat software implemented in JavaScript, PHP and MySQL. Sound support is implemented using Flash, Socket support using Flash on client-side and Ruby on server-side.
There is an AJAX Chat channel for each forum. The list on the right shows the channels that currently have someone using them.