Page callback: Displays add content links for available content types.
Redirects to node/add/[type] if only one content type is available.
function node_add_page() {
$item = menu_get_item();
$content = system_admin_menu_block($item);
// Bypass the node/add listing if only one content type is available.
if (count($content) == 1) {
$item = array_shift($content);
drupal_goto($item['href']);
}
return theme('node_add_list', array(
'content' => $content,
));
}