kopete

Kopete is an instant messenger supporting AIM, ICQ, Windows Live Messenger, Yahoo, Jabber, Gadu-Gadu, Novell GroupWise Messenger, and more.

It is designed to be a flexible and extensible multi-protocol system suitable for personal and enterprise use.
The goal of Kopete is to provide users with a single easy-to-use way to access all of their instant messaging systems. The interface puts people first, and is integrated with the system address book to let you access your contacts from other KDE applications. Instant messaging can be intrusive, but Kopete's notification system can be tuned so that only important contacts interrupt you.
Kopete also features tools to enhance your instant messaging experience, such as message encryption, archiving, and many other fun and useful effects.
Kopete supports all commonly used instant messaging protocols, and the Kopete team provides templates for developers to base new plugins on. The API provides developers with many features to make it easy to support a new protocol. All protocols are plugins and allow for modular installation, configuration, and usage.
If you need help with any of its features, check the Kopete Handbook, accessible from the Help menu, or see the 'Forum' and the 'Userbase' links in the navigation bar. See the 'Communicate' section of the site to get in touch, or you can also always reach the team on IRC (irc.kde.org, #kopete).