CodeCanyon - Shifty Nav - a Fully Responsive JS CSS3 Mega Menu - RIP | 259 KB
Shifty Nav is a fully responsive CSS3 mega menu. It was created using LESSCSS so modification is incredibly simple.
DEMO:
http://codecanyon.net/item/shifty-nav-a-fully-responsive-js-css3-mega-menu/5319528?WT.ac=search_thumb&WT.seg_1=search_thumb&WT.z_author=stoise