Not sure how long a service like this will be available, but it's pretty cool. it's like IRC, but sits in a tiny window anywhere you go at the site. Simply put a gabbly.com/ in front of the address, and you're there. So if you're here at ye olde tfp, just do this
http://gabbly.com/www.tfproject.org. So far it's free.
Edit: it has audio as well, but since I'm at work
can't test that.