This is a new plugin that i have developed. Most of the time, we want to show different widgets for different posts, but WordPress sidebar does not allow us to do that. What this plugin does is to add a dynamic widget to your sidebar. You can configure it to show different widgets for different page/post.
Plugin homepage: http://maketecheasier.com/wordpress-plugins/wordpress-widget-changer
Download link: http://maketecheasier.com/a/wp-widget-changer