Emacs org-mode with babel is definitely the bee's knees.

I can intersperse org-mode markup (much richer than markdown) with syntax-highlighted and executable code snippets. I can export all of this to my wordpress blog or to great-looking LaTeX documents, or even to presentations using org-reveal.

Here's an example of an exported org-mode file with math and graphics: http://vxlabs.com/2014/06/16/level-sets-the-practical-10-min...

Here's a simpler example with just Python snippets embedded: http://vxlabs.com/2014/11/12/getting-django-rest-framework-t...