I’ve spent some time lately hacking on beirc, the McCLIM-optimized CLIM IRC client by Gilbert Baumann. The version you find in the CVS repository at common-lisp.net comes with a neat channel selector that may remind you of xchat. Channels are shown red if there was activity on the channel that you didn’t see yet and blue if there were messages on the channel that contained your nickname.

You can see it in action in this screenshot.

I really like how easy CLIM makes adding new features like this channel selector. The code for the actual selector, including the activity indicator is only a few tens of lines. (the new channel selection mechanism I had to implement is a bit more than that, but that’s GUI toolkit independent)