Markdown by DaringFireball - Text-to-HTML conversion tool/syntax for web writers, by John Gruber
Remember The Milk - Remember The Milk is a task and time management application for mobile devices.
Typora - A minimal Markdown reading & writing app.
Toggl - Toggl is an online time tracking tool. It features 1-click time tracking and helps you see where your time goes. Free and paid versions are available.
StackEdit - Full-featured, open-source Markdown editor based on PageDown, the Markdown library used by Stack Overflow and the other Stack Exchange sites.
TimeCamp - Simple and robust time tracking app to help you stay on the same page with your team while working from home.