IRC never really went away. If you are a participant in the opensource world, there’s a good chance you’ve fired up an IRC client to connect to your project channel (eg. #maria) to chat with people involved with the project.
Slack is becoming really popular, and from what I can tell, it looks very much like IRC. I tried Kik again, when I read Hashtags as Social Networks. This is IRC — with a channel limit (50 users). The twist is that its mobile, since you’re quite happily doing this kind of chat on your mobile phone.