Anki is described as 'Program which makes remembering things easy. Because it is a lot more efficient than traditional study methods, you can either greatly decrease your time spent studying, or greatly increase the amount you learn' and is a leading flashcard learning tool in the education & reference category. There are more than 100 alternatives to Anki for a variety of platforms, including Web-based, Android, iPhone, iPad and Windows apps. The best Anki alternative is AnkiDroid, which is both free and Open Source. Other great apps like Anki are RemNote, Quizlet, Memrise and Mochi.
The official app to compliment Anki for desktop. Syncs with Ankiweb.