Gives you the ability to configure widgets on a per page basis.
XWidgets lets you choose your widget layouts and settings for each individual page and post, instead of only having one layout applied to the whole site! For example, you could have a Twitter feed in your website's sidebar, but have your 'about me' page also display Flickr/Last.FM widgets in that page's sidebar, with a completely different widget layout from the rest of your site -- or you could have each page of your site pull in a different Google News feed via RSS -- or you could add a poll to the sidebar of a specific post, without changing any others.
This plugin was developed alongside the PBox plugin. Using the two together greatly simplifies CMS-like layouts and functionality.