Eggdrop

    The world's most popular open source IRC
   bot, designed for flexibility and ease of use.  Eggdrop is
   freely distributable under the GPL.  It was originally
   developed by Robey Pointer but he no longer works on it.

   Eggdrop is designed to run on Linux, *BSD, SunOs,
   Windows, Mac OS X and other platforms.  It is extendable
   with Tcl scripts and/or C modules.  It supports
   Undernet, DALnet, EFnet, IRCnet, and QuakeNet.  It
   can form botnets and share partylines and userfiles
   between bots.

   (2005-07-07)