How do I view the maintenance page without putting the site in maintenance mode? I've just been asked by the stakeholder of a site I'm working on how he can view the maintenance page of his site so he can test links on it without putting the site in maintenance mode.

I'm going to suggest that we do this in a lower environment, since the info is the same but is there any way to do this?
By default there is no route to access the maintenance page via url. You can create a menu item and the corresponding page callback in your module : 

// Access maintenance page regardless of the maintenance mode. 
$items['maintenance'] = array(
  'title' =&gt; 'Maintenance',
  'page callback' =&gt; 'yourmodule_maintenance_page',
  'access callback' =&gt; 'user_is_logged_in',
  'type' =&gt; MENU_CALLBACK
);

yourmodule_maintenance_page () {
  // Just use the internal status code to make Drupal load the apropriate theme and template. 
  return MENU_SITE_OFFLINE;
} 


And that's all, go to /maintenance to see the page. 

You may also want to override the 'maintenance_page' theme, have a look at :


the base preprocess function in includes/theme.maintenance.inc
base template file in modules\system\maintenance-page.tpl.php