Chat Script / Web Chat

I am currently looking for a chat script what can be integrated in to my site and works flawlessy without any problems. It will support chat rooms, Instant messaging and say whos online. I don't want a login facility in the chat script because the users are authenticated before that. Plus it will be easy to customize the design so it fits in with my site which I can do. A bonus will be if it supports webcam chat. I will only consider scripts that I can see a demo of and what they support and how easy they are to integrate. Thanks