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.
Viber - Free and secure calls and messages to anyone, anywhere. Keep your conversations going no matter where you are.
Adium - Adium is a free instant messaging application for Mac OS X that can connect to AIM, MSN, Jabber, Yahoo, and more.
MiVoice Business - MiVoice Business is a business communication platform that delivers voice, messaging, mobility, presence, conferencing, collaboration and applications.
Gajim - Full featured and easy to use Jabber client
Zoom - Equip your team with tools designed to collaborate, connect, and engage with teammates and customers, no matter where you’re located, all in one platform.