SEO Internal linking (page, post, category). Automatic SEO for website
The WatchCount.com WP Plugin is a free eBay WP plugin that shows Most Popular (or a seller's) eBay items in a blog's sidebar or posts.
Content curation tool to search entries based on the number of terms: display posts without tags, with too many categories, etc.
Adds post-tags functionality for pages.
WordPress plugin to add Category Specific RSS feed subscription menu to your posts, pages and sidebar.
Entering tags for posts each time can be tedious. This plugin will look for existing tags within your content and add them automatically.
Easily assign categories to media with a clean, simple, and searchable category meta box. Then use the gallery shortcode to display category galleries
Tagbag, takes the thought out of selecting tags for your post
Adds a "View" button to the top of an 'edit category'
Creates "choose from most popular sitewide tags" function on post edit screen