Smart Categories is a simple to use WordPress plug-in that will allow you to display the posts from a single category or all the child category posts organized by category inside an existing post or page with no need to modify any php code.  You can see it in action on my fantastic freeware favorites pages.  You’ll notice that everything on the page is hyperlinked, the category, category Rss feed, and all posts.

Installation

1. Download and unzip the smartcategories.zip file.
2. Place the smartcategories.php file into your /wp-content/plugins/ directory.
3. Activate the plugin from the WordPress admin panel.
4. Place the trigger text inside any post to use the plug-in.
5. In WordPress 2.8, Comment out Lines 27,28 in ~\wp-includes\category-template.php
6. The commented out lines should look like this:
   //        if ( is_wp_error( $category ) )
   //            return $category;

Trigger Text Syntax-Display Posts of a Category

%%smartcategories%%#49%%  or  %%smartcategories%%#49#50%%

• The #number is the id of the category that you would like to expand.
• You can have as multiple categories expanded by simply repeating the #number as many times as you need.

Trigger Text Syntax-Display Posts of Child Categories

%%smartcategorieschild%%#49%%  or  %%smartcategorieschild%%#49#50%%

• The #number is the id of the category that you would like to expand.
• You can have multiple categories expanded by simply repeating the #number as many times as you need.

Special thanks goes out to Justin Blanton and his “Smart Archives for WordPress ” plug-in, which gave me  the inspiration to create my Smart Categories and Smart Tags WordPress plug-ins.