Menu Block - How to make a new menu automatically available?
I'm not very familiar with the Menu Block module, but this seems to be the proper way of setting the menu_block_menu_order variable when a new menu is created:

function mymodule_menu_insert($menu) {
  $menus = variable_get('menu_block_menu_order', array('main-menu' =&gt; '', 'user-menu' =&gt; ''));
  $menus[$menu['menu_name']] = '';
  variable_set('menu_block_menu_order', $menus);
}