irssi - Irssi is a terminal based IRC client for UNIX systems.
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
Pidgin - Pidgin is an easy to use and free chat client used by millions. Connect to AIM, MSN, Yahoo, and more chat networks all at once.
Jitsi - Open-source video calling and chat platform.
KVIrc - KVIrc is a free portable IRC client based on the excellent Qt GUI toolkit.
Miranda IM - Miranda IM is the smaller, faster, easier instant messenger with support for multiple protocols.