thoughtbot/trail-map — pull request #34 by garethrees (2012-06-05 14:29:38+00:00)
Title: Start an intermediate Ruby section

Block parameters source: http://blog.codahale.com/2005/11/24/a-ruby-howto-writing-a-method-that-uses-code-blocks/
Hashes source: http://www.jasimabasheer.com/posts/meta_introduction_to_ruby.html