X (Twitter) - Connect with your friends and other fascinating people. Get in-the-moment updates on the things that interest you. And watch events unfold, in real time, from every angle.
memordo - Spaced repetition tool to help you retain more knowledge
SmartCards+ - Spaced Repetition Software for iOS. Modern, powerful and easy to use.
Zorbi - Spaced-Repetition Flashcards - Other tools are built by boomers, Zorbi is built by students.
Harken - Flashcard app using smart repetition to improve your memory
@slashRemindMe - A Twitter bot to remember things or threads