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.
Bip is an IRC proxy that supports replaying logged conversation and multiple clients on one IRC server connection. It has a handy logging directory structure. It is multi-user and has a flexible configuration. Some of its configuration can be changed at runtime with special IRC commands.
Fama IM is a project to build an easy to use, powerful instant messaging software built on the Flexible Communications Framework, Telepathy. The interface is text-based and built upon the ncurses library, hence you run it in your favorite terminal emulator or directly in the console.
irssi-xmpp is an irssi plugin to connect to the Jabber network. It aims to provide good integration in this text-based IRC client. It can send and receive messages in irssi's query windows. A roster is shown for tracking contacts' resources. Contacts can be managed. Command completion, multiple accounts (in different connections), Unicode, and SSL are supported.