For the moment when I want to show a single post without using a loop I use this:
As wordpress api has changed, you can´t use get_posts with param 'post_name'. I´ve modified Maartens function a bit:
function get_post_id_by_slug( $slug, $post_type = "post" ) {
$query = new WP_Query(
array(
'name' => $slug,
'post_type' => $post_type,
'numberposts' => 1,
'fields' => 'ids',
) );
$posts = $query->get_posts();
return array_shift( $posts );
}