Typora - A minimal Markdown reading & writing app.
Xmind - Xmind is a brainstorming and mind mapping application.
StackEdit - Full-featured, open-source Markdown editor based on PageDown, the Markdown library used by Stack Overflow and the other Stack Exchange sites.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
MarkText.app - Mark Text is a Markdown editor for Mac, Windows and Linux.
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.