Slack - A messaging app for teams who see through the Earth!
Mattermost - Mattermost is an open source alternative to Slack.
Tandem - Get fluent together. Practice languages, anytime, anywhere.
Loop Email - Emailing for teams: Organize your Inbox into channels 💌
Opensource Builders - Find open-source alternatives to commercial apps
CAKE - CAKE provides a SaaS-based solution for advertisers, publishers and networks to track, attribute and optimize their spend in real-time.