This plugin allows you to create new widgetized areas in the Appearance > Widgets menu, and insert those widgets into your pages and posts by using the appropriate shortcode. This allows you to get around the auto-formatting of the WordPress editor, which often disables JavaScript code you try to embed from third-party services. You can also use this functionality to create a repeatable piece of content, such as a call to action box, inside a widget. You can insert the shortcode in multiple pages, and if you want to alter that piece of content, you will only need to do it in one place (inside the widget).
For more information, see the plugin page(s):
http://wordpress.org/extend/plugins/widgets-on-pages/