So when WordPress introduced the wp_nav_menu() function, it made it easier to create navigation menus for the average user. You can create dropdown navigation simply moving the items around in the admin -> appearance -> menu section of your dashboard. This tutorial requires jQuery, but is not a jQuery plugin.
Here is a small bit of code to place on your page.php template. If the page id is the parent page that has child pages, this code will generate a dropdown menu of those children only on the pages that meet that criteria.
This is a nice and clean quick tip to create a jump menu without a "go" button. Say for example you have a list of items in a database that need to have a details page based upon their "id". This will create a dropdown menu that is auto populated with the most up to date list.