Server: irc.quakenet.org
Channels:
- #monsterhunt - general monster hunt talking/discussion
- #PMHServer - the servers reporter channel (talk to players who are playing on the server)
Alternatively, if you plan to be on it a lot then I'd suggest getting an IRC client. One of my favorites and free, clients is mIRC. You can get it here: http://www.mirc.com/ I'd suggest reading some documentation and/or posting here on how to get connected.
If you just want to get on for a bit while you play, then you can join throught he built in Unreal Tournament IRC client. Simply click: Multiplayer | Find Internet Games | Chat then enter irc.quaketnet.org in the IRC Server field and change the default channel to #monsterhunt.