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.
Gabber is a Jabber client for GNOME. Jabber is a flexible distributed Open Source instant messaging system. It also happens to allow communication with other instant messaging systems, such as ICQ, AIM, Yahoo!, MSN, and even IRC. Gabber aims to implement quite a bit of Jabber's functionality while remaining easy to use.
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.
OpenGaim is an instant messaging or "text chat" client capable of communicating over many protocols, including Jabber, AOL Instant Messenger (AIM), ICQ, MSN Messenger, Yahoo! Messenger, Internet Relay Chat (IRC), and more. It is a loose relative of the Gaim project and contains much of the source code in Gaim itself. However, OpenGaim aims to provide quicker releases to fix major problems, and advanced customization options and features not available in Gaim.
ImageIM is a plugin for Gaim that lets buddies send screenshots to each other via HTTP. Users can simply click the ImageIM button, select a portion of the screen, and then send their buddy the image. If the buddy doesn't have ImageIM, they will receive a link pointing them to the image.