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.
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.
pork is an ncurses-based AOL instant messenger client. It uses the OSCAR protocol (the one the Windows client uses) to access AIM. Pork features Perl scripting, an online help system, the ability to configure nearly all aspects of the program's look and feel, an alias system, and a powerful, fully configurable key binding system. It supports being logged in with more than one screen name at the same time. The default look and feel of the client is modeled after the ircII IRC client. Anyone comfortable using ircII (or any clients derived from it, e.g. epic, BitchX, etc.) will feel comfortable using pork.
JavaBot is a chat bot for the AOL Instant Messenger, MSN Messenger, and Yahoo! messenger systems. It is designed to attempt to engage in conversation with people via IM. It supports such features as remote administration and full conversation logging. There is also a mechanism for eavesdropping on conversations other people are having with the bot. All administration is handled over IM, allowing remote administration. Using a simple scripting language, the bot's conversational responses can be modified to taste.
LarryMessenger is a simple to install and easy to use cross-platform instant messenger client. It has a nice graphical user interface, and allows people to communicate over a LAN with static IP addresses without the need for a central server. Furthermore, it provides functions to query the ICQ and AIM networks.
AIMSpy is an application that parses and displays content from instant messaging systems using the local network. It is multi-threaded, uses BPF devices for network access, and includes fairly thorough support for the AIM chat protocol and rudimentary support for the Rendezvous (iChat) protocol.