Quizlet - Quizlet allows you to review and create flashcards for a variety of subjects, such as math and reading.
Listmonk - Send e-mail campaigns from a powerful dashboard. High performance and features packed into one app.
Kahoot! - Kahoot! makes it easy to create, play and share fun learning games in minutes—for any subject, in any language, on any device.
Mailman - Mailman is free software for managing electronic mail discussion and e-newsletter lists.
Brainscape - Find, create, and study SMART FLASHCARDS on any device. DOUBLE your learning speed using the most effective study system on the planet. Keep all your content in sync across Brainscape's website and your Android devices.
Sendy - Sendy is a self hosted newsletter app that sends emails 100x cheaper via Amazon SES