Thomas

Really simple plugin that allows you to easily add tooltips to your posts using the shortcode [wpetp].
It was made for some simple tooltips with text and/or images. For example if you want a way to add some information about a word in your post without forcing the user to leave the page to see them.
Feel free to ask for some features if you think I missed some.
Languages: English.

WP Easy Tooltips

Simple plugin that allows you to easily add tooltips to your posts using a shortcode.

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.

WP Easy Tooltips vs WordPress Tooltip