Lately I have been working a lot with YAML data in my HAML templates via Middleman. YAML is great for providing data to display on your site. It allows for easy modification and addition trough separate .yml files instead of having to copy-paste HTML/HAML. YAML is very intuitive to write and work with from Ruby (and templates). But if you are in need of some good documentation, check out this YAML Cookbook.
I'm a 22 years old developer and UI designer from The Netherlands. This is where I share my experiences with mobile and web apps.