Israel Curtis

This framework is a collection of classes and functions for handling advanced custom post types cases. With just a few defined arrays, it can create custom post types, taxonomies, their labels, menus, metaboxes, and save routines.
NOTE: this began life as an internal development tool, and as such, does not have much (if any documentation) just yet. It’s not really end-user friendly in its current state. So if you’re not running a site I have built for you personally, you probably don’t need it 😉

Somatic Framework

Adds useful classes for getting the most out of Wordpress' advanced CMS features

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.

Somatic Framework vs User Taxonomies