I have been looking for this kind of information already, thanks for sharing all you guys with your latest information.
If I were you, I’d follow forum etiquette which would also help you to gain as much exposure to your query as possible. Fire off a new post if you’re not having much luck using the Sitepoint http://www.sitepoint.com/forums/search.php.
Thank you for the tips, everyone! 
But I’ve been doing very well w/ my Volusion free chat software. I recommend it to everyone that’s looking for a free LiveChat program!
I just did some searching on google for you and found “PHPOpenChat” - it looks quite good and is free.
I want to know too… may be a livezilla will be the best bet.
Yahoo Messenger MSN Live both are free live chat software. You can try both of these.
you can try plupper … it’s pretty mature tool with great REST API. You can even create your own chat window.
Livezilla could use some speed improvements - particularly in the cobrowse area - but overall I am pleased and find the real time stats such as referrer string, referrer keyword, # of visit etc. very useful info.