Free WordPress myStickymenu pluginFree
By default, sticky menu is designed to use element class “.navbar” as “Sticky Class”. That value should be modified in plugin settings for different themes to make it work. Sticky Class is actually nothing more than an element class (or id) of the element that should become sticky.
Advancement of this simple plugin is that increases usability and page views of your WordPress site since menu is available to the user all the time.
Plugin is localized (multi language support) and responsive (as far as your theme is). Also there is possibility to add custom css code which make this plugin very flexible, customizable and user friendly.
Plugin is originally designed for Twenty Thirteen template but should work on any theme.
Tags: header,menu,sticky,sticky header,sticky menu
Source from: WordPress.org