MacDown - MacDown is an open source Markdown editor for OS X, released under the MIT License.
Typora - A minimal Markdown reading & writing app.
Frost - An open API for Blockchain timestamping
Markdown by DaringFireball - Text-to-HTML conversion tool/syntax for web writers, by John Gruber
Gingko - Write and organize your ideas in Gingko tree documents.
Dillinger - joemccann has 95 repositories available. Follow their code on GitHub.