appear.in (free and paid options)
This might be the easiest to use app for video meetings currently available.

Brosix Messenger (paid options)
Encrypted messenger for team collaboration. Includes features such as group and private chat, file transfer, screen-sharing, screen-shot, whiteboard and more.

Chalk (free)
Instant, secure voice rooms for chat.

Discord (free)
An invite-only place with plenty of room to talk. Encrypted. Chat via text, voice, or video. Public, private, or semi-private.

ezTalks (free and paid options)
Host audio/video meetings and webinars. Also offers affordable conference room solutions and video conferencing hardware.

Flock (free and paid options)
Group collaboration software and central messaging platform that includes third party integrations, video calling, and more. Cheaper than Slack and has more native features.

Franz (free and paid options)
A messaging app for desktop/laptop that combines multiple chat and messaging services into one application. Currently supports Slack, WhatsApp, WeChat, Facebook Messenger, Telegram, Google Hangouts, GroupMe, Skype and many more. Available as a desktop app for Windows, MacOS, and Linux.

Gotalk (free and paid options)
Group video chat with no login or apps needed!

GroupMe (free)
Create and carry your group messages from one device to another, no app necessary. Owned by Skype (Microsoft).

Jitsi Meet (free)
Fully encrypted, 100% open source video conferencing solution that you can use all day, every day, for free — with no account needed. Share your desktop, presentations, and more. Invite users to a conference via a simple, custom URL. Edit documents together using Etherpad. Trade messages and emojis while you video conference, with integrated chat.

LINE (free and paid options)
Limited free international calls, free messaging. See the fine print for details on the free calls.

Loom (free)
Video messaging for most platforms (iOS, Windows, Mac, Chrome)

Marco Polo (free and paid options)
Free, unlimited, and ad-free. One on one or group chats. Like video voicemail. You can only connect with people whose are in your phone’s contact list. Phone app; available for Android and iOS.

Nextiva (paid)
Send and receive secure electronic faxes from anywhere on any device.

Riot (free)
An open source, universal, end-to-end encrypted chat,. Exchange files, make voice or video calls and conferences, add bots. Own your own data.

Ripcord (free and paid options)
A desktop chat client for group-centric services like Slack and Discord with no tracking or analytics.

Rocket Chat (free and paid options)
Free audio and video conferencing, guest access, screen sharing, file sharing, LiveChat, LDAP Group Sync, two-factor authentication (2FA), E2E encryption, SSO, and dozens of OAuth providers.

Signal (free)
State-of-the-art end-to-end encryption keeps your conversations secure. We can’t read your messages or listen to your calls, and no one else can either. Privacy isn’t an optional mode — it’s just the way that Signal works. Every message, every call, every time.

Slack (free and paid options)
Stay on the same page and make decisions faster by bringing all of your work communication into one place.

Verified Call (free)
A platform that allows anyone to speak to customers and fans via a secure phone connection. Verified Call is easy to set up, safe to use, completely secure, and profitable from the very first call. Each person that uses it is given their own unique VerifiedCall.com URL and profile page in addition to the ability to integrate Verified Call’s technology within their own websites.

Viber (free)
Secure calls and messages to anyone, anywhere. Includes group messaging and chats.

Whereby (free and paid options)
Video meetings and conferences with screensharing. Really simple to use; no app or downloads needed — just use it in your browser.