Pidgin is a GTK2-based instant messenger application. It supports multiple protocols via modules, including AIM, ICQ, Yahoo!, MSN, Jabber, IRC, Napster, Gadu-Gadu and Zephyr. It has many common features found in other clients, as well as many unique features. Pidgin is not endorsed by or affiliated with AOL TimeWarner, Microsoft, or Yahoo.
NetPlug is an extensible multi-connections, multi-protocol, network client program, written in pure Tcl/Tk. Includes a complete Irc client plug in that you should love if you like IrcII 'classic' look & feel (plus customizable style/colors scheme, sound,... Now includes full DCC support (with GUI), ircII like aliases and improved scripting (Tcl!), keywords (your nick...) highlighting, and more
tircproxy is a full featured IRC proxy. It can proxy DCC CHAT, DCC SEND and other DCC requests transparently to the user, block common trojans (such as script.ini), hide the user's identity and more. It can be used with the Linux kernel or IPF transparent proxy features to transparently proxy IRC sessions.
DummyIdentd Server Daemon is a Perl program that accepts identd requests (port 113), and responds with a valid response, but giving out no useful information. It is written in Perl, and is suitable for running on company gateways/firewalls to enable your users to access services such as IRC, which require identd.
IRC Defender is a Perl program for protecting your IRC network against virus drones, general troublemakers, ban evasion, and attacks. It is fully modular, able to unload and load modules on the fly, and comes with several modules to ban anatoly/fyle virus drones, block unauthorised cgi:irc sites, conduct ctcp version surveys, maintain ctcp version blacklists, and (most importantly) set regexp-based akills.
Bouncer is an IRC session manager that can share a single server connection between multiple clients. This makes it possible to run the same IRC session at home or in your office. It also has a flexible plugin structure that allows you to record message and do logging in a centralized place.
SurrealServices is a full replacement IRC Services package providing NickServ, ChanServ, BotServ, MemoServ, and OperServ, as well as LogServ and ConnectServ. Features are loosely based on ConferenceRoom/Auspice and Anope, as well as NeoStats. Some security features are also available such as a TOR (http://tor.eff.org/) detector/banner and a country detector (which checks IP allocation and optionally bans). It is multithreaded to eliminate lag due to the asynchronous nature of MySQL and DNS lookups.