OpenBot is an OpenSource IRC Bot, it's written in Python and it uses Twisted NET FrameWork, so it works on more O.S. (Linux, Windows, MAC, BSD).
Since the main coder and all helpers and testers are Italian the description is written in Italian, but the project language is (almost) written in English, except for few incode comments.
The MainCoder is Luciano Ferraro (aka lux), he's blog: http://ferraro.wordpress.com/
OpenBot's USE guide (in Italian/in Italiano): http://ferraro.wordpress.com/openbot/
OpenBot's Source (SubVersion repository): http://openbot-python.googlecode.com/svn/trunk/