Empathy - Apps/Empathy - GNOME Wiki!
Mumble - Mumble is an open source, low-latency, high quality voice chat software primarily intended for use...
IM+ - Chat everywhere! IM+ is the most widely used mobile IM app! Connect all-in-one to MSN, Yahoo!, Goo...
Vivox - Vivox is called to be one of the leading chatting platforms for online gamers.
Gajim - Full featured and easy to use Jabber client
Discord - Step up your game with a modern voice & text chat app. Crystal clear voice, multiple server and channel support, mobile apps, and more.