by Samer Bechara on WordPress.org
Allows the user to dynamically set the number of posts to show per page on category pages, tag pages, author pages and all other archive pages.
This plugin allows your website visitors to set the number of posts they see per page. It will insert a form at the top of your posts page in order to allow your website visitors to quickly set the number of posts they want to see per page.
Detailed Features
User Posts Per Page allows your website visitors to set the number of posts per page, and remembers that number everytime they reach your website.
Plugin Usage
echo do_shortcode('[user_posts_per_page]');