Use Ruby's marshal facilities in ActiveRecord to serialize some attributes for schema-less awesome.

create_models_migration.rb

class CreateModels < ActiveRecord::Migration
  def change
    create_table :models do |t|
      t.binary :extras

      t.timestamps
    end
  end
end

marshal_store.rb

module MarshalStore
  class NilFriendlyMarshal
    def self.load(str)
      if str.nil?
        return Hash.new
      else
        Marshal.load(str) || Hash.new
      end
    end

    def self.dump(str)
      Marshal.dump(str)
    end
  end

  extend ActiveSupport::Concern

  module ClassMethods
    def marshal_store(store_attribute, options={})
      serialize(store_attribute, NilFriendlyMarshal)
      store_accessor(store_attribute, options[:accessors]) if options.has_key? :accessors
    end
  end
end

model.rb

class Model < ActiveRecord::Base
  include MarshalStore
  # Same API as regular ActiveRecord::Base.store
  marshal_store :extras, :accessors => [:name, :description, :founder_id]
end