Tom Belknap

The ultimate auto-tagging plugin for WordPress.
NOTE: The plugin is now being maintained on GitHub, so please do contribute all your questions, comments, suggestions, fixes and improvements with me <a href="https://github.com/holisticnetworking/title-to-terms" rel="nofollow ugc">here</a>.
Title to Terms Ultimate is for every WordPress admin that needs tags, categories and other taxonomies filled out automatically. For each post type in your WordPress installation, T2TU will allow you to assign a taxonomy to be automatically updated with keywords pulled from the title of the post.
Every time a post gets saved or updated, T2TU analyzes the title of the post for usable keywords. A list of user-configurable “Stop Words” is checked by the parser, so that words like “I” or “going” don’t get made into ultimately useless tags.
<ul>
<li>Converts keywords in post titles to terms in any taxonomy</li>
<li>Includes user-editable list of words to be ignored.</li>
<li>Ignore list can be reset to default at any time.</li>
<li>Converts on save, not publish.</li>
<li>Configurable to either add new terms or append the list of terms.</li>
</ul>
Multisite admins take note: this plugin is especially helpful if you’re building a community-based site where tagging is important and your bloggers are not always diligent about tagging.
<h3>Acknowledgements</h3>
<ul>
<li>The WP Plugin Repository icon and banner were both made with the kind contribution of: <a href="https://thenounproject.com/search/?q=taxonomy&i=165760" rel="nofollow ugc">Muharrem Fevzi Çelik @ The Noun Project</a> (CC licensed)</li>
</ul>

Title to Terms Ultimate

The ultimate auto-tagging plugin for WordPress.

Erick Hitter

Creates dropdown lists of non-hierarchical taxonomies (such as <code>post tags</code>) as an alternative to term (tag) clouds. Multiple widgets can be used, each with its own set of options.
Numerous formatting options are provided, including maximum numbers of terms, term order, truncating of term names, and more.
Using the <code>taxonomy_dropdown_widget()</code> function, users can generate dropdowns for use outside of the included widget.
Only use version 2.2 or higher with WordPress 4.2 and later releases. WordPress 4.2 changed how taxonomy information is stored in the database, which directly impacts this plugin’s include/exclude term functionality.
This plugin was formerly known as the <code>Tag Dropdown Widget</code>. It was completely rewritten for version 2.0.
Follow and contribute to development on GitHub at https://github.com/ethitter/Taxonomy-Dropdown-Widget.

Taxonomy Dropdown Widget

Creates a dropdown list of non-hierarchical taxonomies as an alternative to the term (tag) cloud. Formerly known as Tag Dropdown Widget.

Title to Terms Ultimate vs Taxonomy Dropdown Widget