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.
AIM Sniff is a utility for monitoring and archiving AIM and MSN messages across a network. It can be used to monitor for cases of harassment or warez trading. It has the ability to do a live dump (actively sniff the network) or read a PCAP file and parse the file for IM messages. You also have the option of dumping the information to a MySQL database or STDOUT. AIM Sniff will also monitor for an IM login and then perform an SMB lookup on the originating computer in order to match NT Domain names with IM login names (handles).