libirc++ is a well designed, modern C++ IRC Library. This lib should and can be used as base for IRC Bots and IRC Clients. The library is designed for multiple simulatneous connections so the library can fill any purposes.
MIMA, The Multiprotocol Instant Messenger Annotations Library for Java, provides a simple and unified annotation-driven api for developing messaging business functionality and messenger bots over the AIM, Yahoo, GTalk/Jabber and IRC protocols.
This project provides a basic Java implementation of the OSCAR protocol, used by ICQ and AIM clients. Commonly used features such as messaging, status and server buddy lists are supported, making it easy for developers to use this in their own work.
uIrcBot is a irc bot written in C++ for windows and unix. The bot can publish game-events from a counterstrike game server on an irc channel. The project includes a flexible and easy irc lib which handles the irc-events.
PVCGS - (Lib)Purple Virtual Client Gateway Server (a.k.a. Cuckoo)
A Libpurple based instant messenger gateway server for accessing the messenger services you are subscribed to from many locations at once.