Display data from custom fields

List all pages and then all posts with specific custom field

<?php
$type = 'page';
$args=array(
    'post_type' => $type,
    'post_status' => 'publish',
    'posts_per_page' => -1,
    'meta_key' => 'url',
    'caller_get_posts'=> 1
    );
  $my_query = null;
  $my_query = new WP_Query($args);
  if( $my_query->have_posts() ) {
    echo 'List of: ' . $type .'(s)';
    while ($my_query->have_posts()) : $my_query->the_post(); ?>
      <p><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></p>
     <?php
    endwhile;
  } //if ($my_query)
wp_reset_query();  // Restore global post data stomped by the_post().
?>

Related:
query_posts()
Custom Fields
Page Templates

What should I add if I wanted to display only urls or other cutom fields from subpages of the current page?

Could use the 'post_parent' => $post[0]->ID, argument

$args=array(
    'post_type' => $type,
    'post_parent' => $post[0]->ID,
    'post_status' => 'publish',
    'posts_per_page' => -1,
    'meta_key' => 'url',
    'caller_get_posts'=> 1
    );