Wikidata is the Wikipedia project for structured knowledge. For example it knows that the capital of Spain is Madrid. The ruby gem wikidata has a basic support to retrieve it:
require 'wikidata'
Wikidata::Item.find_by_title('Spain').claims_for_property_id('P36').first.mainsnak.value.entity.label
Categories: Ruby on Rails & other tech
Hector Perez Arenas 