Stephen,
I didn't see much in the way of integrated chatrooms for Geeklog. There are two that I found, but I am not sure how up to date they are.
This one is an full plugin for geeklog:
http://www.geeklog.net/filemgmt/index.php?id=44
This appears to be a bridge between phpMyChat and Geeklog:
http://www.geeklog.net/article.php?story=20040216184110173
Hope this helps.