Anima App - Design, get feedback, convert to code, publish, iterate.
Markdown by DaringFireball - Text-to-HTML conversion tool/syntax for web writers, by John Gruber
Auto-Layout for Sketch - Responsive design for Sketch
Typora - A minimal Markdown reading & writing app.
Sketch Repo - Collection of resources for anyone who uses Sketch
StackEdit - Full-featured, open-source Markdown editor based on PageDown, the Markdown library used by Stack Overflow and the other Stack Exchange sites.