Niraj Chauhan

This plugin will help the user to add a drop-down-custom-taxonomy box with the help of small code on his desired location.
<h4>Options</h4>
just place this small code into your theme file and the drop-down box will appear on that page 
code: 
for example, if you want to display it on home page, 
then navigate to index.php, the inside that put this code, if you want to display the custom taxonomies, then just replace category with your custom taxonomy name.

Drop-down-taxonomy

This plugin will help the user to add a drop-down-custom-taxonomy box with the help of small code on his desired location.

madalin.ungureanu

ReflectionMedia

IMPORTANT: The plugin Custom Taxonomy Creator will no longer be supported or updated.
Custom Taxonomy Creator is now part of <a href="https://wordpress.org/extend/plugins/wck-custom-fields-and-custom-post-types-creator/" title="download link" rel="ugc">WCK – Custom Fields and Custom Post Types Creator plugin</a>, which is fully compatible. <a href="https://wordpress.org/extend/plugins/wck-custom-fields-and-custom-post-types-creator/" title="download link" rel="ugc">Download it</a> and install it instead of the current plugin.
WCK Taxonomy Creator allows you to easily create and edit custom taxonomies for WordPress without any programming knowledge. It provides an UI for most of the arguments of register_taxonomy() function.
Features:
<ul>
<li>Create and edit Custom Taxonomies from the Admin UI</li>
<li>Advanced Labeling Options</li>
<li>Attach the taxonomies to built in or custom post types</li>
</ul>

Custom Taxonomy Creator

With WCK Taxonomy Creator you can create and edit custom taxonomies and attach them to post types.

Drop-down-taxonomy vs Custom Taxonomy Creator