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.
Clearbit - Clearbit provides Business Intelligence APIs
LimeSurvey - LimeSurvey: the Online-Umfrage Tool - Open-Source Suryeys
ZoomInfo - ZoomInfo is a B2B database providing detailed business information on people and companies.
Quizlet - Quizlet allows you to review and create flashcards for a variety of subjects, such as math and reading.
InsideView - InsideView aggregates and curates all the company and contact data, news and social insights, and professional connections you need to do business better.