If you're already familiar with NetBSD, this information may not be particulary new or useful to you. It's not particularly Atari-specific. I do however use this for my own reference when I install NetBSD/atari.
irssi is a lightweight IRC client.
- Make sure to run through the pkgsrc configuration described in the packages section.
- cd /usr/pkgsrc/chat/irssi
- sudo make install
Note: See the irssi documentation for more information on using irssi.