I've been working on a Markdown (Jekyll) > Static HTML site > epub workflow lately. At first I tried to use a jekyll plugin but couldn't get one to work. Wound up needing to do some prep on the files anyways.

I wound up using Pandoc to create the epub. It is really simple. If it would be desirable, we could add epub generation to the "build process" which would give readers another way to access the content offline (i know we may use this workflow for RTFM too).