Pidgin

Next to Trillian, Paltalk or Miranda IM, Pidgin (formerly named Gaim) is a reliable IM software that offers users the possibility to chat on multiple protocols at the same time. It comes with support for a wide variety of instant messaging protocols, amongst which are the following: AIM, ICQ, Google Talk, Jabber/XMPP, MSN Messenger, Yahoo!, Bonjour, Gadu-Gadu, IRC, Novell GroupWise Messenger, QQ, Lotus Sametime, SILC, SIMPLE, MXit, MySpaceIM, and Zephyr.