I have seen it used many times before, but have never implemented it myself. I know the concept behind CoveritLive, a free and easy to use service that allows you to integrate a live chat onto your site or blog.
It also allows you to do much more, such as aggregating tweets. Greg Linch, an online intern @Dallas_News and new media brainchild for journalism, used it today to aggregate tweets from the Personal Democracy Forum 2009 in his blog. I figured I would give it a try by testing the service my self and aggregating the same feed (sorry if I stole the idea, Greg, but I needed something timely).