Check out CHAT AND GO :)
Its an instant messenger that allows a chat in the browser from a personal URL - mine is HERE - you can click on it and chat with me. (If im logged on when you click it)
These personal URLS can be sent by email,so you get somebody's email with a link in the signature,click on the link and chat.
There are also buttons available- there's a cut-n-paste HTML code that can be added to ads,blogs,etc.- these buttons show whether you are offline or online.
This is awesome!!!!!!!!!!