Slack - A messaging app for teams who see through the Earth!
Airtable - Airtable works like a spreadsheet but gives you the power of a database to organize anything. Sign up for free.
9mCollab - Collaborate (efficiently) Conclude (fast) Contribute (in the knowledge base)
Microsoft Teams - Microsoft Teams provides the enterprise-level security, compliance and management features you expect from Office 365, including broad support for compliance standards, and eDiscovery and legal hold for channels, chats, and files.
Mattermost - Mattermost is an open source alternative to Slack.
RingCentral Video - Live life unlimited. Free video meetings and team messaging in one app that works the way you do.