alexhal

The Shop Ajax tags dropdown allows customers to sort products based on tags instead of variations. For example: 
Show all products with tag “Tshirt” or show all products with tag “Jumper” and “Jersey”.
This plugin still needs some development, but if you just need a basic AJAX tag widget it will do. 
We hope to release and updated version in a couple of weeks which works better.
This plugin is compatible with WordPress 4.0 and WooCommerce 2.2.0-bleeding.

Shop Ajax Tags Dropdown

This plugin adds an AJAX tag Dropdown widget to your WooCommerce shop.

zackdesign

Note: This plugin requires PHP 5
Warning: This plugin requires knowledge of CSS to use adequately in widgets
Features at a glance:
<ul>
<li>Widgetised to make it really easy to add multiple dropdowns anywhere on the page you have sidebars</li>
<li>Ability to create the menu wherever you want with PHP Classes</li>
<li>Leverages the new WordPress 2.8 widget settings to allow quick and easy multiple widget instances</li>
</ul>
Theming options:
<ul>
<li>Multi-level dropdown (CSS included)</li>
<li>Multi-level left/right flyouts (CSS included)</li>
<li>Support for Superfish Javascript (CSS included)</li>
<li>Works with other CSS (within reason)</li>
</ul>
If you want me to modify the CSS for you simply <a href="http://www.zackdesign.biz" title="Zack Design" rel="nofollow ugc">contact me</a> and I will do it easily and quickly for you for a moderate sum.
It uses <a href="http://www.cssplay.co.uk/menus/final_drop.html" title="Stu Nicholl" rel="nofollow ugc">Stu Nicholl’s final drop-down code</a> which is a complete CSS solution – no Javascript required!!
You can look on <a href="http://www.cssplay.co.uk/menus/" title="Stu Nicholl's Menus" rel="nofollow ugc">Stu’s site for other drop-down code</a> as I got the flyout left and right code from there. Don’t forget to donate if you’re using his styles.
Most of his CSS should work just fine with the menu. I’ve made it so that the plugin automatically finds menu.css in the plugin’s folder and loads it in your WordPress site so you can instantly see how it will look. If you want to create your own CSS simply create menu.css in your theme’s root directory and the plugin will load that automatically for you.
Please note that if you’re upgrading you will need to change your theme files to suit the new approach. See Installation for further information.

WordPress CSS Drop-down Menu

Use Wordpress' nav menu system to create left/right widget flyouts, with support for Superfish

Shop Ajax Tags Dropdown vs WordPress CSS Drop-down Menu