Duolingo - Duolingo is a free language learning app for iOS, Windows and Android devices. The app makes learning a new language fun by breaking learning into small lessons where you can earn points and move up through the levels. Read more about Duolingo.
Jenkins - Jenkins is an open-source continuous integration server with 300+ plugins to support all kinds of software development
Eduflow - Digital learning that actually teaches students something
CircleCI - CircleCI gives web developers powerful Continuous Integration and Deployment with easy setup and maintenance.
Kialo - Kialo is the platform for rational debate. Empowering reason through friendly and open discussions.
Travis CI - Focus on writing code. Let Travis CI take care of running your tests and deploying your apps.