it’s pretty sweet. you can connect to every IM service known to man, and it even checks all your email, facebook, and twitter too with nice popup notifications!
it only works for windows at the moment, but the guys over there are working hard and pushing out updates very frequently. i’m alpha testing and even so i haven’t seen any crashes or any major problems. there have been the minor quarks here and there, but that’s to be expected when you’re alpha testing. check it out at digsby.com
also, you can embed a chat client into your website…like this: