Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
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.
ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...
LimeSurvey - LimeSurvey: the Online-Umfrage Tool - Open-Source Suryeys
LightShot - The fastest way to take a customizable screenshot.
Quizlet - Quizlet allows you to review and create flashcards for a variety of subjects, such as math and reading.