Usmu is a next-generation static site generator built in Ruby and designed from the ground up to be flexible and extensible but still easy to use.
$ gem install usmu
$ usmu init my-awesome-site
$ cd my-awesome-site
$ usmu serve
# => View at http://localhost:8080/
You can add plugins just by installing the gem:
$ gem install usmu-github-pages
You can see the source code for this website.