# Ever had the trouble to create a new named_scope out of others? See how it works:
class Fu < ActiveRecord::Base
  named_scope :has_moo,  :conditions => { :moo => true }
  named_scope :has_foo,  :conditions => { :foo => true }

  def has_moo_and_foo
    has_moo.has_foo
  end

end

# -> now this works:
# Fu.has_moo_and_foo.all

#  Sweet!