Markdown is an easy to ready text markup that can be easily converted to HTML, PDF, or other formats. Markdown is easier to read than HTML and more portable than Microsoft Word.
Markdown is a simple and beautiful markup for text
Minimalist Markdown Editor for Chrome
http://en.wikipedia.org/wiki/Markdown
https://github.com/dcurtis/markdown-mark
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Markdown was developed by John Gruber of Daring Fireball
MouApp.com a free OSX Markdown editor and preview tool