Creating a Dropdown menu in Drupal 7 My question is how do we get the menu in drop down structure. 
i.e

&lt;ul&gt;&lt;li&gt;&lt;a&gt;&lt;/a&gt;&lt;ul&gt;&lt;li&gt;&lt;a&gt;&lt;/a&gt;&lt;/li&gt;&lt;/ul&gt;&lt;/li&gt;&lt;/ul&gt;


I used following:

&lt;?php print theme('links', array('links' =&gt; $main_menu)); ?&gt;


but this only produces top level menu even if we have sub menus in menu management.
horizontal or vertical nested menus: Nice Menus or Superfish

simple vertical nested menus: Menu Block