BitlBee allows users to talk to people on the major instant messaging and microblogging networks (including MSN, Google Talk, AIM, and Twitter) from within any IRC client by emulating an IRC server. Virtual channels are created with all of the user's contacts in them, who can be talked to in the channel or in a query. Also, one can participate in group chats and chat rooms like they were normal IRC channels.
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.
Licq includes all the basic features of ICQ, like sending/receiving messages, chat, file transfer, contact list with pixmaps and user status, basic/extended user info, adding/editing users from within the GUI, user history, user groups, and new user registration. All commands and information are available through a simple and convenient tab dialog. Licq also has a completely configurable user interface with Skin and Icon pack support. It is written in C++ and comes with a GUI plugin using the Qt widget set. Other plugins are also available, like basic MSN support.
climm (CLI-based Multi-Messenger) is a portable, small, yet powerful console-based ICQ and XMPP client. It supports password changing, auto-away, creation of new accounts, and other features that makes it a very complete yet simple client. It is able to send and receive messages from the ICQ network, list users that are offline and online (including their online status), search for users by email address, and look up basic (name, UIN, email) information. climm was formerly known as mICQ.
sim (simple instant messaging) is an IRC client specialized for use with bitlbee. It is based on sic (http://suckless.org). It reads commands from standard input and prints all server output to standard output. It also multiplexes all channel traffic into one output, so you don't have to switch to different channel buffers. sim must be customized by editing its source code to insert the correct username, server, password, and identification information.
pidgin-osd is an application that uses the xosd library to print various events on the X root window on receiving incoming messages from pidgin. It is based on gaimnosd 0.7 (the last publically available version). It is mostly like the gaimnosd plugin; the only difference is that an implementation for UTF-8 conversion to the current used locale was added.
IM-Filter is a daemon that runs on a firewall and filters ICQ traffic. The daemon can identify file transfers, handle UIN and word blacklists, manage a list with currently logged in users, and log messages sent via the ICQ protocol. The modular design allows implementation of other protocols like MSN or IRC.