Soulseek (http://www.slsknet.org) is a communication and file-sharing system. It is quite similar to Napster: it lets you exchange files, search for files, chat with other users in public and in private, browse their files, and get recommendations for music. SoulSeek for Linux is a GUI client for the system written in Python/wxPython. It includes all the major functionality: chat, searches, and file transfers.
GYach Enhanced is a feature-rich, improved version of the original Gyach. It is the first Yahoo! client for Linux with voice chat capabilities. It offers almost all of the features you would expect to find in the official Windows Yahoo! client. The program offers support for chat, conferences, buddy lists, and My Yahoo content. In addition, Gyach Enhanced offers many features not available in the official Yahoo! clients for Windows, Mac, and Linux. Webcam support is under development and planned for the future. Unlike the original Gyach, GYach Enhanced is designed for Linux only.
Akeni Instant Messaging Server Pro is a client/server instant messaging platform that allows companies to host their own secured private IM system. The client has an user interface similar to AIM, ICQ, or MSN Messenger. It supports all the standard IM features such as chat, group conference, presence management, file transfer, offline messages, and emergency alert/notification. Extra features include contact management and optional tabbed chat sessions. The server has advanced administration tools for managing user accounts, client-side logging capabilities, and peer-to-peer file transfers. It can be set up on a private network without connecting to the Internet, and can easily be set up for use inside and outside of the company firewall.
Akeni LAN messenger is a cross-platform instant messenger client. It is a P2P program that works on your LAN without the need of an Internet connection or a dedicated server. The client has an user interface similar to AIM, ICQ, or MSN Messenger. It supports all the standard IM features such as chat, group conference, presence management, file transfer, and emergency alert/notification. Extra features include contact management and optional tabbed chat sessions.
MudMagic Mud Client is a GTK/GNOME multi-platform MUD client. It provides aliases, triggers, multiple connections, plugins, MCCP, ZMP, MSP, tabbed sessions, ANSI color, and a game list that can be updated from mudmagic.com. It is configurable on a per-session basis. Plugins include an automapper, database, and note pad.
JTelIRC is an advanced IRC framework for Java. It is mainly intended for writing automated clients ("bots"), but may be used for normal clients as well. It provides an intuitive and well documented Java interface to IRC and makes it extremely easy to write advanced clients quickly.