http://www.123flashchat.com An easy to install but nicely done chat server. You can download the demo version for free and host your own chat server. The chat server can be intergrated into phpnuke, phpBB, postnuke, etc. The server is fast, though you will lose connection if you are using the demo version. Also, there are great supports on that site, you can ask the admins on that site whenever you have any problem.