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.

FuzzGuard

This plugin allows you to display widget items based on if a user is logged in, logged out or based on the role you have given the user.
This plugin allows fine-grained permissions to be added to each individual widget item to display or not display the item based on the 
 users logged in/logged out status or the role assigned to the user. This solves the problem of having to modify theme functions.php files to add in widget restrictions. The changes in functions.php is often overwritten by a theme update. This plugin removes that worry, as you can update the theme, independent of the plugin.

Privilege Widget

This plugin allows you to display widget items based on if a user is logged in, logged out or based on the role you have given the user.

Galaxius Custom Sidebars vs Privilege Widget