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);
}
}