Jitsi Desktop (previously SIP Communicator) is a legacy audio/video and chat communicator with full encryption, precedessor of Jitsi Meet .
Jitsi Desktop is not actively developed anymore: last version, released in October 2017, can be still downloaded from GitHub. Its successor is Jitsi Meet
WhatsApp is an iPhone and Android messaging app which allows you to exchange messages without having to pay for SMS.
Wire is the most secure collaboration platform featuring messenger, voice, video, conference calls, file-sharing, and external collaboration –all protected by the most secure end-to-end-encryption.
Zulip is the only modern team chat app that is designed for both live and asynchronous conversations. Zulip topics create a separate space for each discussion, so different conversations will never get in each other's way.
Video conversations with up to 8 people in your browser - no downloads, no login. Just name your channel and you are on. Works in all modern browsers, even mobile.
LINE is a Japanese proprietary application for instant messaging on smartphones and PCs. Line users exchange text messages, graphics, video and audio media, make free VoIP calls, and hold free audio or video conferences.
Paltalk is an instant messaging service that enables users to communicate via internet chat, voice and video chat. It offers chat rooms and the ability for users to create their own public virtual chat room.
Tango allows you to easily connect with friends & family or make new friends. Make video & voice calls, send text messages, play games, send music messages powered by Spotify and more all for free.
Mapple.me bridges the gap between available time and availability of friends to increase social contacts in real life by simply using the mobile device in your pocket. Even with those friends you might not think of or you‘ve lost touch with.