Haystack Search - Haystack helps you make the most of your time, by searching all your files and documents in the cloud in one place. It's been built for privacy from the ground up, so your data isn't stored on a server, just your computer.
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.
MailJack+ - Send PDFs as postal mail
markdown to web - Convert markdown to online web page
Paperkit - Create and download custom graph, lined, or dot grid paper
Mochi - Write notes and flashcards with Markdown and study them with spaced repetition.