gnuBot is an IRC bot written in Perl, designed to be as flexible and easy to use as possible. Dynamically loadable modules are used for everything from networking to configuration, allowing parts to be swapped out at will. It is intended to be both a channel service bot, like an eggdrop, but also have infobot-like features.
Hybserv2 is a new and improved version of the now unsupported Hybserv, sporting new features, bugfixes, and more. It is specifically designed for Hybrid IRC servers, but may work with others as well. It includes OperServ, NickServ, ChanServ, MemoServ, StatServ, HelpServ, and Global. Each of the services can be enabled and disabled as necessary.
infobot is an IRC bot written in Perl 5 which implements a sort of artificial intelligence by learning information ("factoids") from channel discussions and then responding intelligently to queries about this accumulated information. It also acts as a gateway to other useful sources of information (e.g. online dictionarys/weather stations, internic WHOIS database, DNS, IMDB, slashdot headlines, search engines, other infobots).
ircbase allows you to establish a persistent IRC server connection on any UNIX box with 24/7 day connectivity much like an advanced bot, then attach to it from any machine to allow control of it and use it much like a normal IRC client. ircbase has advanced scripting capabilities (including optional Python support) and is intended to be able to fully replace bots and ircbouncers, as well as provide an advanced IRC platform, which can fully support any GUI.