Not a company guy, just a student at Northeastern University's CS school. We have an IRC channel, but it's tough to explain to freshmen how to ssh into a university box and use screen+irssi, and then get them to keep doing it. If they use Windows you also have to show them how to set up PuTTY. I'm not against teaching people how to do this, but teaching this doesn't scale. That's why our IRC channel is mostly upperclassmen and alumni.

Now whenever we need to coordinate for student groups (like ACM) we use Facebook groups and Facebook chat (which is XMPP, so I plug my account into Adium).

I'm working on a guide to screen+irssi to get more people on our IRC server, but still I'd trade our IRC&Facebook setup for something like Grove.io or Hipchat.