Do you keep a simple blog, where you don’t define specific categories for your posts but simply let them all be uncategorized and use tags instead? Do you, like me, feel that all the categorizing stuff comes in the way of your content and your blog? Do you feel that keeping only one category seems superflous, but WordPress just forces you to? Then this plugin might be for you!
This plugin is mostly cosmetic, as it doesn’t change or actually remove any categories, but hides any options to change them, so all posts are in fact put in the default category (usually “Uncategorized”). This currently includes the category section on the edit pages and the “Manage categories” section on the admin pages. Published posts will not mention categories, and the Category widget has been removed.
As it doesn’t actually remove the categories or modify any files, this plugin will not affect any other plugins’ usage of categories. This means “Uncategorized” will show up on statistic pages, etc.

No Categories

Simply disables the usage of categories in your WordPress blog.

Marios Alexandrou

Ultimate Category Excluder, abbreviated as UCE, is a WordPress plugin that allows you to quickly and easily exclude categories from your front page, archives, feeds, and searches. Just select which categories you want to be excluded, and UCE does all the work for you!

Ultimate Category Excluder

Ultimate Category Excluder allows you to quickly and easily exclude categories from your front page, archives, feeds, and search results.

No Categories vs Ultimate Category Excluder