QuizUp - QuizUp gives you the opportunity to test your trivia skills against friends and strangers throughout the world.
MacDown - MacDown is an open source Markdown editor for OS X, released under the MIT License.
2016 Photo Challenge - Take a photo every day for 366 days
Frost - An open API for Blockchain timestamping
Woolah - Knockout Photo challenges with your friends.
iA Writer - Minimal Design, Maximum Focus