adding meta info to contents and filter them
Have you looked at the Internationalization module?


  This is a collection of modules to extend Drupal core multilingual
  capabilities and be able to build real life multilingual sites. Some
  features:
  
  
  Taxonomy translation (both, per language terms and translatable terms)
  Multilingual variables Multilingual blocks (control visibility per
  language and translate title and content)
  Language selection (when you switch the site language you'll see only the content for that
  language)
  Requires Variable module 2.x (Drupal 7)
  Read a complete
  feature overview in the Internationalization handbook: Building
  multilingual sites .
  


If you dont want a full i18n site you can always just use a custom field or Taxonomy term and Views to build page lists of content tagged with that language.