Haris Zulfiqar

WordPress tooltip plugins lets you add tooltips to plain text and links on your post and pages.
It offers a tinyMCE shortcode GUI which will guide you through the entire process of a tooltip.
This plugin uses jQuery tipTip authored by Drew Wilson http://code.drewwilson.com/entry/tiptip-jquery-plugin.
You can also add tooltips manually by following the pattern below:
<pre><code>[tooltip content="This will show in a tooltip" url="This will make tooltip a link"]Hover over me for tooltip[/tooltip]
</code></pre>
Url is optional. If URL is added, it will render a link otherwise it will be a plain text.

WordPress Tooltip

WordPress tooltip lets you add tooltips to content on your posts and pages.

techotronic

Adds tinytips tooltips to links on your site. Comes with 8 different themes. 
The tinytip can be added to a link using the WordPress visual editor.
The plugin can be automated to add the functionality for all links.
Tinytips tooltips are added for all links that have a “title” attribute.
See the <a href="http://www.techotronic.de/plugins/jquery-tinytips/" rel="nofollow ugc">plugin page</a> for demo pages.
For more information visit the <a href="https://wordpress.org/extend/plugins/jquery-tinytips/faq/" rel="ugc">FAQ</a>. 
If you have questions or problems, feel free to write an email to blog [at] techotronic.de or write an entry at <a href="https://wordpress.org/tags/jquery-tinytips?forum_id=10" rel="ugc">the jQuery Tinytips WordPress.org forum</a>
Localization
<ul>
<li>English (en_EN) by <a href="http://www.techotronic.de/" rel="nofollow ugc">Arne Franken</a></li>
<li>German (de_DE) by <a href="http://www.techotronic.de/" rel="nofollow ugc">Arne Franken</a></li>
</ul>
Includes <a href="http://plugins.jquery.com/project/tinytips" rel="nofollow ugc">Tinytips</a> 1.1 jQuery plugin from <a href="http://www.mikemerritt.me/" rel="nofollow ugc">Mike Merritt</a>. 
Tinytips is licensed as <a href="http://www.mikemerritt.me/plugins/tinyTips/license.txt" rel="nofollow ugc">free of charge for anyone</a>. 
jQuery Colorbox uses the jQuery library version 1.4.2 bundled with WordPress 3.0.

jQuery Tinytips

Adds tinytips tooltips to links on your site. Comes with different themes.

WordPress Tooltip vs jQuery Tinytips