Messaging & Chat - Pidgin
Pidgin - is a multi-protocol instant messaging (IM) client for Linux, BSD, MacOS X, and Windows. It is compatible with AIM and ICQ (Oscar protocol), MSN Messenger, Yahoo!, IRC, Jabber, Gadu-Gadu, SILC, GroupWise Messenger, and Zephyr networks. Pidgin users can log in to multiple accounts on multiple IM networks simultaneously. This means that you can be chatting with friends on AOL Instant Messenger, talking to a friend on Yahoo Messenger, and sitting in an IRC channel all at the same time. Pidgin supports many features of the various networks, such as file transfer, away messages, typing notification, and MSN window closing notification. It also goes beyond that and provides many unique features.