Terry Chay

This allows you to create a simple image mouseover feature by adding properties to an image:
It understands the following attributes which can be added to the HTML:
<ul>
<li>img.class=”mouseover” (activates IMG mouseover for this image)</li>
<li>img.oversrc (If specified, this rewrites the image on mouse rollover)</li>
<li>img.clicksrc (If specified, this rewrites the image on mouse click)</li>
<li>img.noresize (If set, this will make the image have the natural dimensions instead of the dimensions of the original image).</li>
<li>a.class=”mouseover” (activates A tag as a controller for another image, when clicked a class “selected” is tacked on)</li>
<li>a.for (Should be specified to point to target image. Image must be class mouseover)</li>
<li>a.for_link (If specified the ID of a link is replaced with this one)</li>
<li>a.src (If specified, the click will replace the image with this)</li>
<li>a.oversrc (If specified, the click will replace the image mouse rollover with this)</li>
<li>a.clicksrc (If specified, the click will replace the image mouse click with this)</li>
</ul>

IMG Mouseover

Embed a mouseover image into a regular image tag without resorting to hacky inline Javascript.

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.

IMG Mouseover vs jQuery Tinytips