Microdata and Fivestar

Microformats are going to be big, they are big even today. Drupal is caching up but modules don't work properly. First thing you would probably do is ratings/review formating. You can try with microformat and fivestar module but it will not work properly. So I themed the fivestar summary function differently and added few lines and not it works and you can check it with google tool

http://www.google.com/webmasters/tools/richsnippets

Just copy this to your template.php or use some diff tool to see what is different
http://www.quickdiff.com/

function mytheme_fivestar_summary($variables) {
  $microdata = $variables['microdata'];
  extract($variables, EXTR_SKIP);
  $output = '';
  $div_class = '';
  $average_rating_microdata = '';
  if (isset($user_rating)) {
    $div_class = isset($votes) ? 'user-count' : 'user';
    $user_stars = round(($user_rating * $stars) / 100, 1);
    $output .= '<span class="user-rating">'. t('Your rating: <span>!stars</span>', array('!stars' => $user_rating ? $user_stars : t('None'))) .'</span>';
  }
  if (isset($user_rating) && isset($average_rating)) {
    $output .= ' ';
  }
  if (isset($average_rating)) {
    $div_class = isset($votes) ? 'average-count' : 'average';
    $average_stars = round(($average_rating * $stars) / 100, 1);
    if (!empty($microdata['average_rating']['#attributes'])) {
      $average_rating_microdata = drupal_attributes($microdata['average_rating']['#attributes']);
    }
    $output .= '<span class="average-rating">'. t('Average: <span !microdata>!stars</span>', array('!stars' => $average_stars, '!microdata' => $average_rating_microdata)) .' <meta itemprop="rating" content="'.$average_stars.'" /> </span>';
  }
  if (isset($user_rating) && isset($average_rating)) {
    $div_class = 'combo';
  }

  if (isset($votes) && !(isset($user_rating) || isset($average_rating))) {
    $output .= ' <span class="total-votes">'. format_plural($votes, '<span>@count</span> vote', '<span>@count</span> votes') .'<meta itemprop="votes" content="'.$votes.'" /></span>';
    $div_class = 'count';
  }
  elseif (isset($votes)) {
    $output .= ' <span class="total-votes">('. format_plural($votes, '<span>@count</span> vote', '<span>@count</span> votes') .')<meta itemprop="votes" content="'.$votes.'" /></span>';
  }

  if ($votes === 0) {
    $output = '<span class="empty">'. t('No votes yet') .'</span>';
  }

  $output = '  <div itemscope itemtype="http://data-vocabulary.org/Review-aggregate"><div class="fivestar-summary fivestar-summary-'. $div_class . '">'. $output .'</div></div>';
  return $output;
}