Kevin Langley Jr.

Add widgets on a post by post basis by using a new interface directly on the post edit screen.
Filter to set the post types the Post Widgets plugin should load on post_widget_post_types

Voce Post Widgets

A better interface for managing your widgets.

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.

Voce Post Widgets vs Privilege Widget