Blog-post: http://object.io/site/2011/01/rails-data-import/

import-with-progress.rb

def run_import_step step_name
  report_progress "Running #{step_name}" do
    ImportModel.transaction do
      self.send(step_name)
    end
  end
  //...

importer.rb

def import_updaters
  all_steps.each do |step_name|
    run_import_step(step_name)
  end
end

private

def run_import_step step_name
  puts "Running #{step_name}"

  ImportModel.transaction do
    self.send(step_name)
  end

rescue => e
  STDERR.print "\nImport error:  #{e.inspect}\n#{e.backtrace.join("\n")}"
  STDERR.print "Please resume at step #{step_name}"
  exit 1
end

protected

def all_steps
  [
    :link_frobnitz,
    :spin_really_fast_around_z_axis,
    :reticulate_splines,
    :deploy_hamsters
  ]
end

progress.rb

def report_progress message, &block
  STDERR.print message

  if block_given?
    time = Benchmark.measure { yield }
    formatted_time = "%.2fs" % time.real

    STDERR.puts " - #{formatted_time}"
  else
    STDERR.puts
  end
end