Efnet
The oldest and one of the largest irc networks in the world.
http://www.efnet.org
Dalnet
Dalnet
http://www.dal.net/
Feeenode
Feeenode
http://freenode.net/
IRCnet
Internet relay chat network ircnet homepage.
http://www.ircnet.org/
Rizon
Rizon
http://www.rizon.net/
QuakeNet
The official website for quakenet irc network
http://www.quakenet.org/
Undernet
Undernet
http://www.undernet.org/