This plugin adds in a template tag you can use to display categories and sub categories and the posts underneath those categories.
Installation is simple. Just unzip into your plugins folder and activate the plugin. From there, you may call the function ronalfy_list_categories_and_posts. This function call will be from within a WordPress page template.
An example page template called "sitemap.php" is included in the zip file. You can copy this file into your themes directory and use it as a page template for your sitemap if you wish.
The function by itself will return the categories and posts. It will accept most of the same arguments as
wp_list_categories, but not all of them.