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.

SuperNotecard - Introducing SuperNotecard. SuperNotecard is an online writing tool that features virtual notecards to help arrange facts or scenes, track details, organize paragraphs, and clarify your composition process.

Cram - Cram is an app for Android, Windows and Apple devices that allows you to search for flashcards in a range of topics to study for an upcoming test or to learn new information. Read more about Cram.

Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.

RemNote - All-in-One Tool For Thinking & Learning

Freeplane - Freeplane is a powerful and free software for building mind maps.