Jason Corradino

This plugin will make it quick and easy for your writers to select categories related to what they are writing. As they type in the search box, categories will be shown and hidden in real time, allowing them to easily select what is relevant to their content without having to scroll through possibly hundreds of categories.

Searchable Categories

Searchable Categories allows a quick real-time search through categories while selecting in new post/edit post view.

Matthew Muro

Restrict Categories is a plugin that allows you to select which categories users can view, add, and edit in the Posts edit screen.
This plugin allows you to restrict access based on the user role AND username.

Restrict Categories

Restrict the categories that users can view, add, and edit in the admin panel.

Searchable Categories vs Restrict Categories