Woolah - Knockout Photo challenges with your friends.
MacDown - MacDown is an open source Markdown editor for OS X, released under the MIT License.
SPAR! - Challenge your friends. Put money on the line. Get better.
Frost - An open API for Blockchain timestamping
ShutterSpots - Find & share photo locations nearby & all over the world!
Typora - A minimal Markdown reading & writing app.