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.
GitHub Polls - Polls for GitHub issues and readme
LanguageBeast.com - Study English synonyms and antonyms to enrich your vocabulary
Octotree - Github on steroids
Skeebdo - Learn English words from any movie/TV show
Metaverse - Democratized augmented reality platform: AR for everyone!