An IRC channel would be nice. I don't think people would use a chat room as actively as an IRC channel.

IRC is excellent.. I always have IRC on.. it's not like MSN, it's a chatroom with many people in the same room. Some people are moderators (ops), some are regular chatters, others are distinguished (often by a +)
It's all REAL-TIME.

I'm always on the server-group called EFNET, on the following "channels" (chat rooms):

#3dsmax (3d studio max)
#3dsmax.no (norwegian channel)
#brønnøysund (the channel for my city)
#f4wtrivia (trivia / quiz with 200`000 questions, and hiscores)

I always have it on, whether I'm in the house or not.
If anyone wants to message me, he can message me privately, and I don't need to be present, I can read what he wrote when I come back.

A good IRC program is MIRC
www.mirc.com