Slack - A messaging app for teams who see through the Earth!
Zoom - Equip your team with tools designed to collaborate, connect, and engage with teammates and customers, no matter where you’re located, all in one platform.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
Mattermost - Mattermost is an open source alternative to Slack.
WebEx - Cisco WebEx Web Conferencing, Online Meetings, Desktop Sharing, Video Conferencing