ajberasategui

This plugin provides a Search Widget similar to the default WordPress one but with the abilty of adding category select 
lists to restrict the search query to only those categories.
Any comments, reviews, support questions are very much welcome!!!

AB Categories Search Widget

Insert a search form widget that allows visitors to add category filters to the search query.

DjZoNe

This plugin was born because there was a no other real alternative to enable content sparationd and some CMS like functionalities in WordPress. 
The main goal was, to enhance WordPress’s functionalities, to hide some unwanted categories, from defined parts of the blog.
Today, ACE can override your search results, your RSS feed listing, your category listing, your recent post, and recent post widgets and also your entry page, or even hide whole categories of posts from web crawlers if you want to. 
This is great, for SEO reasons, for content separation, for grouping information, and handle them as real sub pages.
<a href="https://downloads.wordpress.org/plugin/advanced-category-excluder.1.4.5.zip" rel="nofollow ugc">Download now!</a>
<a href="http://ace.dev.rain.hu/" rel="nofollow ugc">Support</a> | 
<a href="http://ace.dev.rain.hu/faq/" rel="nofollow ugc">FAQ</a> | 
<a href="http://djz.hu" rel="nofollow ugc">DjZoNe</a> | 
<a href="https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=paypal@djz.hu&item_name=Advanced%20Category%20Excluder%20for%20Wordpress" rel="nofollow ugc">Donate</a>
Some functions:
<ul>
<li>Integration with Google (XML) Sitmap Generator plugin </li>
<li>Effective category management</li>
<li>Effective content separation </li>
<li>Enables CMS-like functionality</li>
<li>RSS feed manipulation</li>
<li>Search result manipulation </li>
<li>Category list manipulation</li>
<li>Support for Event Calendar </li>
<li>Handles multiple link categories</li>
<li>noindex, nofollow web crawler options for robots – great for SEO </li>
<li>Own Recent Comments, Recent Posts and Categories widgets have been added </li>
<li>Backward SQL compatibility with MySQL 4.0</li>
<li>Nice control panel, called ACE Dashboard</li>
<li>Localization added (swedish, french and hungarian translation included)</li>
<li>Bundeled POT file for translators</li>
<li>WordPress 2.7 UI</li>
</ul>

Advanced Category Excluder

The No.1 content separator, content manager, content excluder, sidebar widget manager plugin to enable CMS like functionality.

AB Categories Search Widget vs Advanced Category Excluder