Supybot is a very flexible and extendable IRC bot written in Python. Here are some plugins I have written for it.
Evaluates expressions in various scripting languages.
This plugin is not secure, so do not load this on any channel where anyone may have malicious intentions.
Maintains a database of users' titles, pronouns, genders, and orientations.
Generates random numbers and makes random choices for you.
(This is the sample module built by following the steps in the plugin creation tutorial.)
Maintains a list of interesting articles, videos, games, and other links
users have found around the Internet.
Schedules reminders, which are posted to the channel at a later time.
Reminders can be directed at yourself or at another user.
Posts links to xkcd comics.