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.

justin

The Unique URL Authentication plugin is a new plugin from Multinc that works with the Social Access Control plugin to add access control 
to syndicated feeds. Since popular web feed readers such as Google Reader do not support private feeds that require a login and a password, 
a common solution is to give each registered user their own unique and unguessable feed URL. With this plugin installed, each user will have 
his or her own feed and will receive a listing of only the feed items that he or she has access to.
Also, the links contained in each feed item and each email notification that point back to the blog website can also benefit from password-less 
authentication. This allows sensitive posts to remain on the website rather than sent out, while giving authorized users single-click convenience.

Unique URL Authentication

Give each registered user their own unique and unguessable feed URL

Privilege Widget vs Unique URL Authentication