Rob Saurini

If you have more than one category associated with a post, how do you tell which category takes precedence? This plugin gives you the ability to promote the category to the main one on the post edit page.
This gets stored in post meta for later use. Soon, I will add some simple functions that will allow you to get the main category on the front end.
Use
<ul>
<li>You can use the shortcode [rs_print_main] inside the post to print out the category title.</li>
<li>In the theme, you can use rs_get_main_category_id( $post_id ) to return (not print) the id of the main category.</li>
</ul>

RS Simple Category Selector

Gives you the ability to promote categories associated with a post.

Marios Alexandrou

DigitalME

As the name suggests this plugin will completely remove the mandatory ‘Category Base’ from your category permalinks ( e.g. ‘mysite.com/category/my-category/’ to ‘mysite.com/my-category/’ ).
The plugin requires no setup or modifying core wordpress files and will not break any links. It will also take care of redirecting your old category links to the new ones.
<h4>Features</h4>
<ol>
<li>Better and logical permalinks like ‘mysite.com/my-category/’ and ‘mysite.com/my-category/my-post/’.</li>
<li>Simple plugin – barely adds any overhead.</li>
<li>Works out of the box – no setup needed.</li>
<li>No need to modify WordPress files.</li>
<li>Doesn’t require other plugins to work.</li>
<li>Compatible with sitemap plugins.</li>
<li>Compatible with WPML.</li>
<li>Works with multiple sub-categories.</li>
<li>Works with WordPress Multisite.</li>
<li>Redirects old category permalinks to the new ones (301 redirect, good for SEO).</li>
</ol>

No Category Base (WPML)

This plugin removes the mandatory 'Category Base' from your category permalinks. It's compatible with WPML.

RS Simple Category Selector vs No Category Base (WPML)