Psi+ Project — development branch of Psi XMPP client
Psi is a cross-platform powerful XMPP client designed for experienced users. Psi+ is a development branch of Psi XMPP client. Project purpose: collection, refinement and writing new patches for transfer them to Psi upstream developers.
A multi-protocol instant messaging app for Mac OS X
Adium is an Open Source, multi-protocol instant messaging application for Mac OS X. Adium supports AIM, ICQ, Jabber, MSN, Yahoo!, Google Talk, Bonjour, Gadu-Gadu, Novell Groupwise, SIP/SIMPLE (Text), and Lotus Sametime. Additionally, it supports all of these applications at once so, even if you have multiple IM accounts, you don't have to log into each account separately.