TrueFalse

Plugin automatically fills the ALT attribute in HTML IMG tag on every insert a new image into the post, if it is not full.
Note 1. “AFI” does not attribute alt attribute to the images added to the media library.
Note 2. On the role of ALT attribute for the search engines read here:
<ul>
<li>http://help.yandex.com/images/?id=1112581</li>
<li>http://support.google.com/webmasters/bin/answer.py?hl=en&answer=114016</li>
</ul>

ALT for images

Automatic insertion of alt attribute header-based embedded image.

Blackbam

Slick Slideshow is a highly customizable, but easy-to-use JQuery Slideshow Plugin, to show dynamic images or contents on your website. 
Visit the <a href="http://www.blackbam.at/blackbams-blog/slick-slideshow" rel="nofollow ugc">Plugin Page</a> to see it in action.
Inspired by a tutorial from <a href="http://sixrevisions.com/tutorials/javascript_tutorial/create-a-slick-and-accessible-slideshow-using-jquery/" rel="nofollow ugc">sixrevisions.com</a>, we adapted the 
extended work from <a href="http://blog.monnet-usa.com/?p=276" rel="nofollow ugc">Blog Monnet USA</a>. Our part was finally to create a WordPress-Plugin from that.
Features:
<ul>
<li>All Styles, Animation Parameters and Contents are customizable easily over the backend</li>
<li>Can use Image URLs (unexperienced users) or custom HTML (experienced Users)</li>
<li>Valid XHTML 1.0 Strict, Valid CSS 2</li>
<li>Compatibility to other JQuery WordPress Plugins (you can use a Lightbox like Colorbox for example for images in the Slideshow)</li>
<li>Fast and efficient</li>
<li>Does not require extra-tables in your database (actually this might be required one day, but currently everything works fine)</li>
<li>GPLv2 licensed as it is a requirement of the WordPress Codex (donations for the efforts and further development are fair and welcome)</li>
<li>Languages: English, German</li>
</ul>
<h3>Known issues</h3>
<ul>
<li>The Plugin is not tested in combination with the use of other Javascript-Frameworks than jQuery (like Prototype). There might obviously be compability issues.</li>
</ul>

Slick Slideshow

Slick Slideshow is a highly customizable, but easy-to-use JQuery Slideshow Plugin, to show dynamic images or contents on your website.

ALT for images vs Slick Slideshow