Psi is the premiere Instant Messaging application designed for Microsoft Windows, Apple Mac OS X and GNU/Linux. Built upon an open protocol named Jabber, this is a fast and lightweight messaging client that utilizes the best in open source technologies.
Psi is able to interoperate with other, proprietory messaging systems such as AOL´s ICQ and Microsoft´s Messenger. You can keep in contact with your friends, regardless of whether they use AIM, ICQ, MSNM or YahooM. It´s even possible to use Internet Relay Chat!