DaisyNav - jQuery plugin that handle responsive navigation in good way.
This plugin contains pretty cool built-in css for navigation, you can use it on your website, or use your own styles - it's no matters.
DEMO: http://demo.circlewaves.com/daisynav/ - open thi page on the mobile device or just resize window and see what happens with navigation!
Learn more at official plugin page: http://circlewaves.com/products/freebies/daisynav-responsive-dropdown-navigation/