centericq is a text mode menu- and window-driven IM interface that supports the ICQ2000, Yahoo!, AIM, IRC, MSN, Gadu-Gadu, and Jabber protocols. It allows you to send, receive, and forward messages, URLs, SMSes (both through the ICQ server and email gateways supported by Mirabilis), contacts, and email express messages, and it has many other useful features. An internal RSS reader and a LiveJournal client are also provided.
dircproxy is an IRC proxy server ("bouncer") designed for people who use IRC from lots of different workstations or clients, but wish to remain connected and see what they missed while they were away. You connect to IRC through dircproxy, and it keeps you connected to the server, even after you detach your client from it. While you're detached, it logs channel and private messages as well as important events, and when you reattach it'll download those logs to you using ordinary IRC protocol.
Fugu is a standalone, graphical client for the Gale instant messaging system. It is fully featured and supports all common Gale messaging operations. In addition, Fugu features a Windows port, multiple screens for different subscription lists, clickable URLs, thumbnail pictures showing the sender of each message, and configurable notification when new puffs arrive.
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.
Keep in Touch aims to be a secure IM system for multiple platforms. It supports its own XML-based protocol as well as ICQ and AIM (toc). It provides encrypted connections between the server and client aswell as encrypted chat on all supported networks. The client can store contacts on the server allowing users to keep their contact lists between different locations.
KVirc is a Visual Internet Relay Chat Client based on the Qt library. Features include a MDI user interface, drag & drop, built-in scripting language (aliases, popups and events), customizable backgrounds and colours, DCC (chat, send with resume, voice), CTCP functions, mIRC colour support with preview, notify list, online help and configurable logging.