AndrewUlrich

This plugin creates two widgets:
<ol>
<li>A widget where you can choose from all the categories in your blog.</li>
</ol>
This is similar to what newegg.com uses, where you can select multiple categories, and it will only show posts belonging to all the categories you select, and such categories can be narrowed down by selecting their subcategories.
<ol>
<li>A widget where you can choose from all the tags in your blog</li>
</ol>
You can select the tags you want to search for, and it will only show posts that have all of the tags you selected.
<h3>Known Issues</h3>
After upgrading from 2.1 to 2.2 it is highly recommended that you deactivate the plugin and then re-activate it. Unfortunately WordPress 3.1 no longer calls register_activation_hook when the plugins are upgraded, so this may be necessary, otherwise you may not see all your categories.
When using version 3.2 or above, and excluding categories, the display order may or may not be mixed up when you exclude a parent category.

Faceted Search

This plugin will create widgets that you can use to conduct faceted searches using the categories or tags on your site.

Marzio Carro

Adds categories and tags functionality for your pages.
This plugin addsthe ‘post_tag’ and the ‘category’ taxonomies, which are the names of the existing taxonomies used for tags and categories the Post type ‘page’.
This enables the categories metabox and the tags metabox in the New or Edit Page interface.
The plugin has no settings, does not alter the database and only uses hooks to 
achieve it’s goal. It works perfectly fine with Multisite installations.
This plugin WILL NOT add any display of categories or tags to your template files.
Plugin’s website: <a href="http://technotes.marziocarro.com/category/wordpress-plugins/" rel="nofollow ugc">http://technotes.marziocarro.com/category/wordpress-plugins/</a>
Author’s website: <a href="http://technotes.marziocarro.com/" rel="nofollow ugc">http://technotes.marziocarro.com/</a>

Category Tag Pages

Wonderful functionality

Yes, it works. Uses very few lines of code and it's a simple and safe solution to have categories and tags in pages.

It works

Adds categories and tags functionality for your pages.

Faceted Search vs Category Tag Pages