Gyach is a GTK+-based Yahoo! Chat client which can use your existing Yahoo! logins for chatting in Yahoo! Chat. It supports colors, emotes/aliases, PMs, set status, remote user status display, ignore lists (local, non-Yahoo! based), a regex list of triggers to cause users to be automatically ignored, command-line recall via arrow keys, and tab completion of usernames.
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.
icqlib is the most feature complete, open source, library implementation of Mirabilis' ICQ protocol available on the Internet. It currently supports most of the ICQ UDP v5 and ICQ TCP v2 protocols, including new UIN registration, chat, and file transfer. It was written in C for portability, and supports multiple simultaneous connections to ICQ servers, SOCKS5 firewalls for both UDP and TCP protocols, an event-driven, non-blocking interface, and the Russian language (automatically performs conversion from Windows 1251 encoding to Unix koi8 encoding).
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.