Freenode

The IRC network formerly known as Open Projects Network. It is especially popular among open source programmers.

Homepage: http://freenode.net/

Wikipedia has a channel on Freenode: #wikipedia. Some other wikipedia pages described the channel as belonging to irc.openprojects.net: it is the same network, before the name change. The old address doesn't work anymore. The new one is irc.freenode.net.