Quizlet - Quizlet allows you to review and create flashcards for a variety of subjects, such as math and reading.
Blinkist - Key insights from 6,000+ bestselling books and podcasts
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.
Four Minute Books - Making you smarter in 4 minutes or less.
Brainscape - Find, create, and study SMART FLASHCARDS on any device. DOUBLE your learning speed using the most effective study system on the planet. Keep all your content in sync across Brainscape's website and your Android devices.
StoryShots - Read, watch or listen to bestsellers in minutes. For FREE.