add_action('init','random_add_rewrite');
function random_add_rewrite() {
global $wp;
$wp->add_query_var('random');
add_rewrite_rule('random/?$', 'index.php?random=1', 'top');
}

add_action('template_redirect','random_template');
function random_template() {
if (get_query_var('random') == 1) {
$posts = get_posts('post_type=post&orderby=rand&numberposts=1');
foreach($posts as $post) {
$link = get_permalink($post);
}
wp_redirect($link,307);
exit;
}
}

/random/
/index.php?random=1