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.

vinaysankhyan

iWR tooltip plugin lets you add tooltips to your post or page or in your template file via a shortcode 
[iwrtooltip title=”this will show in a tooltip”]hover over me to see tooltip[/iwrtooltip] or via a HTML Tag 
<a class=”normalTip” title=”this will show in a tooltip” href=”#”>hover over me to see tooltip</a>

iWR Tooltip

iWR tooltip plugin lets you add tooltips to your post or page or in your template files.

WordPress Tooltip vs iWR Tooltip