Marcin Pietrzak

Display cool, animated fly-out or fade box with related content.
When a reader scrolls to the bottom of a single post, page, or custom post type, an animate box will be shown allowing the reader to select the previous or random available post or posts in the selected configuration:
<ol>
<li>Just previous</li>
<li>Previous in category</li>
<li>Previous in tag</li>
<li>Random</li>
<li>Related using YARPP (only post/pages)</li>
</ol>

upPrev

Great plugin. Works great, lightweight and doesn't take a lot of resources to manage. 

Great Plugin

Display cool, animated fly-out or fade box with related content.

Flector

You can use this plugin to hide part of the text of a post in a nicely-formatted container that will becomes unhidden when clicked on. The plugin can be useful for creating FAQ pages, hiding large pictures, and things like that.
The plugin creates its own “Spoiler” button in the visual editor, but you can also add spoilers directly using tags. For example:
<pre><code>[spoiler title='Title']Spoiler content[/spoiler]
</code></pre>
or
<pre><code>[spoiler title='Title' collapse_link='no']Spoiler content[/spoiler]
</code></pre>
If you liked my plugin, please rate it.

BBSpoiler

This plugin allows you to hide text under the tags [spoiler]your text[/spoiler].

upPrev vs BBSpoiler