Stories - Master complex materials through short daily stories.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Glean.co - Personalized learning for educational video lessons
Learn Anything - Search Interactive Maps to Learn Anything
Mochi - Write notes and flashcards with Markdown and study them with spaced repetition.
Airbnb - Book unique places to stay and things to do.