Autumn Leaves: A Ruby IRC Bot Framework
(image credit: energymech - a cool C-powered bot)
Autumn Leaves is a "full-featured framework on top of which IRC bots can be quickly and easily built," developed by Tim Morgan. It provides everything you need to get an IRC bot up and running, with facilities for loading, daemonizing and logging bots out-of-the-box. Tim says Autumn Leaves has a "Rails-like approach" and presents some example code for building your first bot.