galaxiusmons

This allows you to quickly create a unique sidebar for any post, page, category page or for all posts belonging to a category. You simply enter a name for the sidebar when you create or edit a post, page or category. Browse to Appearance -> Widgets, find your new sidebar and add some widgets to it.

Galaxius Custom Sidebars

Allows quick creation of unique sidebars for posts, pages and categories.

Andrico

A wonderful plugin to easily create many custom sidebars. These sidebars can then select in the creation of a post / page / custom post type / category / taxonomy. We give an order, and select several at once. 
You will see all active sidebars instead of seeing just one.
VISIT https://wordpress.org/plugins/advanced-widgets/
Español:
Un maravilloso plugin para poder crear fácilmente muchos sidebars. Estos sidebars luego los podremos seleccionar en la creacián de un post / page / custom post type / category / taxonomy. Podremos darle un orden, y seleccionar varios a la vez. 
Se verán todos los sidebars activos.
VISITAR https://wordpress.org/plugins/advanced-widgets/

Multiple Sidebars

A wonderful plugin to easily create many custom sidebars. These sidebars can then select in the creation of a post / page / custom post type / categor …

Galaxius Custom Sidebars vs Multiple Sidebars