I can never remember the best way to embed a video in Markdown, so here, for posterity is the information.
If we combine the markup for an embedded image and a link, we can insert an image with a link:
[![alt text](http://darenmay.com/headshot.png)](http://darenmay.com/post "post title")
Taking this approach, we can create clickable images that navigate to a YouTube video:
[![Blinking LEDs](http://img.youtube.com/vi/XAMVzS13HY0/0.jpg)](http://www.youtube.com/watch?v=XAMVzS13HY0 "Blinking LEDs")
Which results in:
There is a great app that does this for you: http://embedyoutube.org/