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.

Zorbi - Spaced-Repetition Flashcards - Other tools are built by boomers, Zorbi is built by students.

Eduflow - Digital learning that actually teaches students something

SmartCards+ - Spaced Repetition Software for iOS. Modern, powerful and easy to use.

Backchannel Chat - Backchannel Chat is best in class discussion tool that is intended for teachers to streamline their class activities.

Mochi - Write notes and flashcards with Markdown and study them with spaced repetition.