remm

<p>This plugin provide widget that display a list with categories and posts in your sidebar.<br />
Widget can save the opened categories, and use cache.</p>


Wp Ajax Tree

This plugin provide a widget that display a category and pages tree on your sidebar, using ajax to collapse categories.

aoulmderat

<p>If you need to add more css and customization options to the Default WordPress Category Widget this plugin is for you.<br />
Using this plugin you can display your sidebar categories in a tree-view in just one click.</p>
<h4>Features</h4>
<ul>
<li>The selection state is preserved (the parent category remain open)</li>
<li>Fully customized and easy to use</li>
<li>Display as dropdown or tree-view</li>
<li>Dynamically create your website tree for all posts & categories</li>
<li>Ability to hide/show count</li>
<li>Ability to hide/show child</li>
<li>When a child is selected The parent category is also selected</li>
</ul>


Display Categories Tree

for performance the css is loaded only when needed

Minimum style and js

This plugin is a widget to customize and add more css options to the Default Wordpress Category Widget. This plugin requires fontawesome in your theme …

Wp Ajax Tree vs Display Categories Tree