This should work:

$args = array(
    \'post_type\' => \'attachment\',
    \'numberposts\' => -1,
    \'post_status\' => null,
    \'post_parent\' => 0
); 
$attachments = get_posts($args);

if ($attachments) {
    foreach ($attachments as $post) {
        setup_postdata($post);
        the_attachment_link($post->ID);
    }
}