Gaim

Gaim is an Internet Messenging client that enables you to chat with others in real time using any supported network, including AIM, ICQ, MSN, Yahoo!, IRC and Jabber. Gaim can be simultaneously connected to several networks, so you can talk with all your contacts via one easy-to-use program.

Gaim supports many native network features, such as file transfer, away messages, buddy icons, typing notification, and MSN window closing notifications, as well as many unique features. There are also plugins available for text replacement, extended message notification, spell checking, tabbed conversations, and more.

This application requires the GTK+ toolkit which you should install first. Click to install directly or read more here.