Are you looking for a plugin that can do this job? Then you came to the right place.
Wordpress is mainly a blogging platform, however it is very common to use Wordpress as a CMS. As of right now, Wordpress does not include the option to reorder categories, pages or posts. This is usually one of the basics of a CMS and it is needed in many situations.

Here are three plugins that extend Wordpress functionality and allow you to reorder links, categories and pages:

My Link Order

My Category Order

My Page Order

Cheers!