In some cases I prefer to edit files using Markdown rather than Org Mode. Marked App works great for previewing Markdown and quickly sharing or saving in various formats.

The Marked Bonus Pack contains a bit of Lisp for sending my current Emacs buffer to Marked for preview…

(defun markdown-preview-file ()
  "use Marked 2 to preview the current file"
   (format "open -a 'Marked' %s" 
       (shell-quote-argument (buffer-file-name))))
(global-set-key "\C-cm" 'markdown-preview-file)

Now I just hit “C-c m” and the current buffer is instantly previewed in Marked App. Nice.