I just came across Gabbly…  Very slick.

It’s a chat application that gathers all the current visitors of the same Web
page.  The concept isn’t exactly new, but my hat’s off for technical
execution.  It’s very slick and super easy to set up:  just tag the
domain name of your destination after
) and you’re in business.

Of course, the real challenge is to make it viral:  right
now, only people who use that redirected URL will join the channel.  You can
embed the application on you Web page, though, so that’s a start…