Mats Westholm

Add one or more Custom Taxonomy to your wordpress managed website.
This plugin is focused on an easy to use interface with small number of choices to make it easier to use for a non technical user.
MW Taxonomy let you choose
<ol>
<li>Taxonomy name in plural and singular,</li>
<li>slug</li>
<li>select the post types (default and custom) where your custom taxonomy can be used</li>
<li>select wheather it should be hierarchical or not</li>
<li>select wherher the taxonomy should be indexed by search engins or not</li>
</ol>
MW Taxonomy includes a widget Custom Taxonomy List for presenting taxonomies in the blog. You need to use a theme that supports widgets for this, that is a classic (non-block) theme. Use the plugin <a href="https://wordpress.org/plugins/classic-widgets/" rel="ugc">Classic Widgets</a> if you don’t find the widget.
Taxonomies can also be presented by Tag Cloud widget or menus (classic theme).
Works in multisite environment as well.
<h4>Docs & Support</h4>
Please ask support questions in the plugin [support forum].(https://wordpress.org/support/plugin/mw-taxonomy)

MW Taxonomy

Easy to use wordpress plugin to add a custom taxonomy

Amaury Balmer

WordPress 3.1 and up allow for reasonably simple custom taxonomy, this plugin makes it even simpler, removing the need for you to write any code.
Add support for taxonomy with or without hierarchical. Choose the selector type for write post.
Allow to add taxonomy to any objects registered on your installation. This plugin can be coupled with the plugin ACF to a new term meta database that allow to create on fly any field need for the taxonomy. For example, for a “Number” taxonomy, you can add fields : number ID, date of parution, screenshot, etc !
This plugin is developped on WordPress 3.5, with the constant WP_DEBUG to TRUE.
This plugin allows you to add taxonomy just by giving them a name and somes options in the backend. It then creates the taxonomy for you, takes care of the URL rewrites, provides a widget you can use to display a “taxonomy cloud” or a list of all the stuff in there, and it allows you to show the taxonomy contents at the end of posts and excerpts as well. 
To boot, it comes with a set of template tags for those who don’t mind adapting their own theme.
For full info go the <a href="https://github.com/herewithme/simple-taxonomy" rel="nofollow ugc">Simple Taxonomy</a> page.

Simple Taxonomy

WordPress 3.1 and up allow for reasonably simple custom taxonomy, this plugin makes it even simpler, removing the need for you to write any code.

MW Taxonomy vs Simple Taxonomy