feed.rb

class Feed < ActiveRecord::Base
  has_many :subscriptions
  has_many :users, :through => :subscriptions
  belongs_to :owner, :class_name => "User"
end

subscription.rb

class Subscription < ActiveRecord::Base
  belongs_to :user
  belongs_to :feed
end

user.rb

class User < ActiveRecord::Base
   has_many :subscriptions
   has_many :feeds, :through => :subscriptions
   has_many :owned_feeds, :class_name => "Feed", :source => :owner
end