This is a good site for improptu meetings (chat only) that need to be set up in a hurry. Some teams may want to use it, if only part of the team has access to other synchronous meeting tools (Skype is blocked at some institutions, I think).
Although this article is about the use of Twitter in the classroom to provide a backchannel for discussion during lectures, I find that the Chat tools in MOODLE work really well for students who are in my face-to-face sessions. They love the possibility of chatting during class (with my permission--and they are aware of my monitoring the discussion), and students who must miss class staying home with a sick child, etc. can ask questions and get answers from students who are in the session.
Thanks Radney for this. I found this article very useful especially the quote "the integration of Twitter has been a virtually bureaucracy-free endeavor". I also liked this "Twitter helps to overcome the shyness barrier" - a good point.
Yes, the shyness factor is a major one in engaging students in class activities. I find that the more text-based the participation, the more engaged shy students become.