Mumble - Mumble is an open source, low-latency, high quality voice chat software primarily intended for use...

Collabify - Easy online meetings, video conferencing and screenshare.

Discord - Step up your game with a modern voice & text chat app. Crystal clear voice, multiple server and channel support, mobile apps, and more.

TeamTalk.io - TeamTalk provides 1 - click meetings, audio -video calling, screen sharing, audio recording...

RaidCall - Free & Light. Setting up is fast and easy; with no need to rent or set up servers. Low CPU usage and minimum memory footprint allows for smooth, uninterrupted communication. im. Group Communication.

FireRTC - FireRTC is the easiest way to call from your computer for free