A couple of markdown cheatsheets:

• https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet

• GitHub Flavored Markdown (GFM) https://help.github.com/articles/github-flavored-markdown/

• http://nestacms.com/docs/creating-content/markdown-cheat-sheet

• http://assemble.io/docs/Cheatsheet-Markdown.html