Download decks for Anki or study directly in your browser.
Anki is a free and open-source flashcard program that utilizes spaced repetition. Spaced repetition increases efficiency by ensuring you review information just before you would forget it.
Official Website • AnkiDroid (Android) • AnkiMobile (iOS) (paid) • Source Code
You can load the downloaded .apkg files into any popular Anki software (Anki Desktop, AnkiDroid, AnkiMobile).