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.
12min APP - Free reading app for summaries of nonfiction books.
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.
Four Minute Books - Making you smarter in 4 minutes or less.