Retrieve a list of Rails 3 Controllers (or any other entities)

rails_3_list_of_entities.rb

# Replace "app/controllers" for the kind of thing you are looking for
# A list of available items can be found in rails/railties/lib/rails/engine/configuration.rb#line39

Rails.configuration.paths["app/controllers"].expanded.inject([]) do |controllers, dir|
  controllers += Dir["#{dir}/**/*_controller.rb"].map do |file| 
    file.gsub("#{dir}/", "")
        .gsub(".rb", "")
        .camelize
        .constantize
  end
end.uniq