I’ve installed a new text-based IRC client called weechat (version 0.2.6) on Blinkenshell. It’s a bit similar to irssi from what I’ve heard, but supports a couple of cool new features such as horizontal split of windows (which allows for features like a neat nicklist.)
It seems to support most other features of irssi, even the more advanced stuff. You can also extend it via plugins written in perl, python (yay!), ruby and lua.
Here’s a screenshot of me running weechat-curses (the ncurses ui) at Blinkenshell: http://independence.blinkenshell.org/dump/weechat1.png
More screenshots are available at the website.
You can try it out yourself, just log in to blinkenshell and type: