I just released and deployed Jekyll 0.7.0 to GitHub Pages today. This release includes support for SmartyPants via RDiscount for Markdown files. To get all those nice curly quotation marks, em/en dashes, and elipses, simply make sure your Jekyll repo’s _config.yml contains the following lines:

markdown: rdiscount
  extensions: [smart]

Then, push your repo to GitHub and enjoy some automatic fancy typographical elements!

NOTE: SmartyPants will only be active on pages written with Markdown.