CleverDeck - Learn languages more efficiently with spaced repetition
Kanji Book - Learn Japanese online with kanji mnemonics. Study all of the jōyō kanji with the best spaced repetition system. It's easier and better than any flashcard app.
ACT Flashcards from Magoosh - Everything you should have learned in high school
Anki - Anki is a program which makes remembering things easy. Because it's a lot more efficient than traditional study methods, you can either greatly decrease your time spent studying, or greatly increase the amount you learn.
LaTeX Cards - The mobile app to create cards to learn your formulas and theorems using LaTeX.
LearnObit - A tool for your learning, like Anki & Workflowy in one