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.

Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.

Quizlet - Quizlet allows you to review and create flashcards for a variety of subjects, such as math and reading.

Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.

Memrise - Learn a new language with games, humorous chatbots and over 30,000 native speaker videos.

Qiqqa - Qiqqa is a free research and reference management software. It can be used in many organizational projects from the academic to the personal to the business endeavor. Read more about Qiqqa.