Joseph Hinson

Do you have a lot of categories and are sick of having a huge list in your sidebar? Want to highlight only a few of them to make your site easier to navigate?
While redesigning WordPress sites for our clients we kept running into this problem over and over. They had a huge list of legacy categories but only wanted to highlight a few of them. We wrote this plugin to allow them to select which categories to show and which categories to initially hide.
All categories are still accessible by a “see all” link at the bottom of the list.
Add the widget to your sidebar to make it live.

Category Expander

Allows WordPress Admins to show only a selected few categories on the sidebar and hide the rest from view until visitor clicks "See All".

zxdong262

This plugin uses jQuery to expand or collapsable the set of posts for each category, 
uses ajax to get the expandable content from server.
0.WHY i do this.
in my work,i need a widget like this,so l learned to write it. 
and i fully tested it in my site,it works fine. 
since i am newbie,so there might be some bug or problem i do not know, 
i appreciate it if you let me know.
1.About the Current Post
if the current post is in the category,the category link will has a “zxd_current_cat” class, 
i certainly can add the css file in this little plugin,but i will not,because it is ugly. 
you can customize it in your theme css file,like
sidebar .zxd_current_cat{
<pre><code> font-weight:bold;
 color:#08c
</code></pre>
}
2.Suggestion
more clean way to use this widget is set it in your theme’s function.php. 
if you want to know how,visit http://html5beta.com/wordpress/wp-ajax-cllapsing-categories/, 
i will explain it there.
<h3>Known bugs</h3>
none
<h3>License</h3>
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

WP ajax Collapsing Categories

This plugin uses jQuery to expand or collapsable the set of posts for each category, uses ajax to get the expandable content from server.

Category Expander vs WP ajax Collapsing Categories