mustansir

This plugin allows you to add a dashboard widget that manages specific taxonomies (Such as tags and categories or any custom taxonomy). Specifically the dashboard widget makes it easy to remove a post from a taxonomy of any kind.
Those who have themes, plugins, widgets that use the wordpress taxonomy system to place posts in various lists will find this plugin especially useful.
This plugin allows you to add a dashboard widget that manages taxonomies. It easy to remove a taxonomy term applied to a post.

Category Manager

The WP Category Manager plugin makes it easier to manage any taxonomy that is used to control the posts within widgets in the presentation layer

Damian Gostomski

This plugin extends the default taxonomy functionality and extends it to users, while automating all the boilerplate code.
Once activated, you can register user taxonomies using the following code:
<pre><code>register_taxonomy('profession', 'user', array(
 'public' =>true,
 'labels' =>array(
 'name' =>'Professions',
 'singular_name' =>'Profession',
 'menu_name' =>'Professions',
 'search_items' =>'Search Professions',
 'popular_items' =>'Popular Professions',
 'all_items' =>'All Professions',
 'edit_item' =>'Edit Profession',
 'update_item' =>'Update Profession',
 'add_new_item' =>'Add New Profession',
 'new_item_name' =>'New Profession Name',
 'separate_items_with_commas'=>'Separate professions with commas',
 'add_or_remove_items' =>'Add or remove professions',
 'choose_from_most_used' =>'Choose from the most popular professions',
 ),
 'rewrite' =>array(
 'with_front' =>true,
 'slug' =>'author/profession',
 ),
 'capabilities' => array(
 'manage_terms' =>'edit_users',
 'edit_terms' =>'edit_users',
 'delete_terms' =>'edit_users',
 'assign_terms' =>'read',
 ),
));
</code></pre>
Read more about <a href="https://codex.wordpress.org/Function_Reference/register_taxonomy" rel="nofollow ugc">registering taxonomies in the codex</a> 
This is heavily inspired by previous work by <a href="http://justintadlock.com/archives/2011/10/20/custom-user-taxonomies-in-wordpress" rel="nofollow ugc">Justin Tadlock</a>

User Taxonomies

Simplify the process of adding support for custom taxonomies for Users. Just use register_taxonomy and everything else is taken care of.

Category Manager vs User Taxonomies