Work n enjoy
This is the website of the Work n Enjoy, a company that believes that the colaborative work is very close to open source.
All the website content is here, you can edit and then request a pull request.
If you go in the list issues, actually you will find demands for this project, that you can be assigend and paid having a account on http://gitpay.me.
What we use
We use Github Pages hosted in a custom domain (http://www.worknenjoy.com) and Jekyll for choose the theme.
Jekyll is a Ruby framework that github supports to generate dinamic pages. If you know Wordpress (http://www.wordpress.com) I can tell you that it uses PHP in a Apache server. So Github host a complete website using Jekyll as template language.
The language is simple and is made by configuration files and plain html, css and js files.
Here are some projects that have used this Jekyll Theme: