Nifty - Manage projects, work, and communications in one place.

Tree - Write documents in tree-like organisation with Markdown

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.

NotePlan - Make plans inside an individual markdown note for every day in your calendar. Use it as a journal for your daily tasks and plan todos in advance. For Mac, iPhone and iPad.

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.

Markdown New Tab - Write notes in Markdown directly in the 'New Tab' page