active_record_extensions.rb

module ActiveRecordExtensions

  module ClassExtensions

    # Returns +Array+ of all +ActiveRecord+ model classes
    def models
      Dir.glob(Rails.root.join('app', 'models', '**', '*rb')).each do |model|
        ActiveSupport::Dependencies::Loadable.require_or_load model
      end
      Object.subclasses_of ActiveRecord::Base
    end

    # Returns +Array+ of all invalid records.
    # Useful for sanity checking in migrations.
    def invalid_records
      returning [] do |invalids|
        (self == ActiveRecord::Base ? models : [self]).each do |model|
          if model.table_exists?
            model.find_in_batches(:batch_size => 100) do |records|
              records.each { |record| invalids << record unless record.valid? }
            end
          end
        end
      end
    end

  end

end

Thought I'd throw this out to the Internets, someone might find it useful.