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.

Zorbi - Spaced-Repetition Flashcards - Other tools are built by boomers, Zorbi is built by students.

Jira - The #1 software development tool used by agile teams. Jira Software is built for every member of your software team to plan, track, and release great software.

Mochi - Write notes and flashcards with Markdown and study them with spaced repetition.

Virtuagym - Virtuagym is a unique, all-in-one fitness solution tailor-made for fitness businesses of all sizes...

SmartCards+ - Spaced Repetition Software for iOS. Modern, powerful and easy to use.