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.

RemNote - All-in-One Tool For Thinking & Learning

Duolingo - Duolingo is a free language learning app for iOS, Windows and Android devices. The app makes learning a new language fun by breaking learning into small lessons where you can earn points and move up through the levels. Read more about Duolingo.

Flashcard Hero - Mac flashcard study app that saves you time memorizing information by keeping track of what you already know so you can focus on what you don't know.

AnkiDroid - Memorize anything with AnkiDroid!

POLAR - A powerful document manager for Mac, Windows, and Linux for managing web content, books, and notes and supports tagging, annotation, highlighting and keeps track of your reading progress.