memordo - Spaced repetition tool to help you retain more knowledge

Synonymful - Improve your vocabulary and communicate like a pro.

Harken - Flashcard app using smart repetition to improve your memory

Reji - Improve your vocabulary hassle-free 📚

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

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.