Mumble - Mumble is an open source, low-latency, high quality voice chat software primarily intended for use...
qTox - A Qt graphical user interface for Tox.
Discord - Step up your game with a modern voice & text chat app. Crystal clear voice, multiple server and channel support, mobile apps, and more.
Tox - Send messages, files, create groups and make Tox to Tox audio and video calls. Securely.
GSC - With GSC, you can pick from any of 14 worldwide datacenters to host your own free voice server.
Toxic - Toxic is a client with an ncurses interface, written entirely in C.