Facebook Style Instant Message Chatbox
 

I'd kill for a chatbox, which goes in the bottom right of the screen (like with facebook), which tells you which of your friends (you'd have to become friends to chat) are online. You then can send instant messaging with that person. No real need for detailed description, just check it out on facebook. :rolleyes:

google cometchat. its what you're looking for. beware though its VERY resource intensive and will bog down your server if your site has people on it.

Be aware of that if you want to run cometchat, your site should be on a dedicated server not less to work properly