Channels and networks. It's been a long time since I've been on IRC. I was an admin on IRCHighway forever ago, but then I just had less and less time for IRC. It's funny because the thing that kept me interested wasn't chatting with anyone on the network about anything, but instead the meta of chatting ABOUT the network, its health, suffering DDoS attacks, learning about servers and getting into web development, and the friends I made along the way. It was a lot of fun, but work and school got in the way. I don't know if I'd go back to IRC or not, but maybe.
I'm sure DALnet and Efnet are still around, and probably still massive. I believe IRCHighway is still around. Maybe it's time to just search the channel list for any interesting ones.