product.rb

class Product < ActiveRecord::Base
  belongs_to :company

  has_many :features,
           :class_name => 'ProductFeature',
           :source => :product_feature,
           :include => :feature

  attr_accessible :description,
                  :name,
                  :company

  validates :company,
            :presence => true
end

product_feature.rb

class ProductFeature < ActiveRecord::Base
  belongs_to :product
  belongs_to :feature

  delegate :name, 
           :to => :feature

  attr_accessible :value
end