JQuery Expanding Box is a WordPress plugin by Hit Reach that reates a shortcode to add an expandable box to show and hide the selected content on a post or page with customisable show and hide links.
Sample code output of the plugin and expand all text
This is the perfect solution for content such as FAQs and Spoilers, where you may not want to show the content to begin with, but prompt the reader to show the content instead.
Download: http://wordpress.org/extend/plugins/jquery-expanding-box/