Today, one of my students asked me to join the channel he created in IRC (DalNet server). It's been a while since i played IRC. My first contact with IRC when i was in high school. It's a great application, since i met my current girlfriend via IRC
At that time, the biggest server known was DalNet, but nowadays, people often choose Freenode because many open source project uses that server instead of the DalNet. I usually go to ##slackware because i'm a Slackware users. I believe many Linux users have their own channel at Freenode too.
Students nowadays don't like and don't know how to use IRC because they are used to IM-based application such as YM or MSN, but IRC is also fun actually when you know how to use them