Good idea…
There is a bunch of chat scripts here:
http://www.hotscripts.com/PHP/Scripts_and_Programs/Chat_Scripts/index.html
Possibly x7chat (no flicker on refresh, supposedly fast)
http://www.hotscripts.com/Detailed/28331.html
voodoo chat tested with up to 450 simultaneous users
http://www.hotscripts.com/Detailed/15084.html
chatness simple and very fast
http://www.hotscripts.com/Detailed/15667.html