This is the source for my personal website and blog.
It is served by GitHub Pages using Jekyll, the combination of which is detailed here by Jekyll and here by GitHub. There is also a guide on making a blog with GitHub Pages and Jekyll here, amongst others.
To render the site at the domain scottclowe.com, I used an Apex Domain (A) DNS with the registrar to point the URL to the GitHub pages page corresponding to this repository (ordinarily at http://scottclowe.github.io).
Details on rendering the site at a custom domain name can be found on GitHub's help pages.
Incidentally, if you were to clone the source for this website, you could compile and browse the site locally using the command
bundle exec jekyll serve
(Although you may want to disable Disqus and Google Analytics beforehand, by commenting out their lines in _config.yml.)
Jekyll will tell you the local port at which you're serving the site, which should be something like http://127.0.0.1:4000/.
This all assumes you've installed Jekyll using RubyGems.
The theme is a modified version of Beautiful Jekyll (see demo) by @daattali.