Makoto

This plugin allows you and your visitors to add comment as textual annotations to images by select a region of the image and then attach a textual description, the concept of annotating images with user comments. 
The text is intergrated with WordPress comment system. 
Integration with <a href="http://www.flipbit.co.uk/jquery-image-annotation.html" rel="nofollow ugc">JQuery Image Annotation from Chris</a> with <a href="http://github.com/stas/jquery-image-annotate-php-fork" rel="nofollow ugc">PHP support from GitHub</a>. 
Modified from <a href="http://www.superwhite.cc/demon/image-annotation-plugin" rel="nofollow ugc">Demon Image Annotation version 1.0</a>. 
Icons from <a href="http://www.famfamfam.com/lab/icons/silk/" rel="nofollow ugc">Fam Fam Fam</a>
Features:
<ol>
<li>Ability to add notes to your uploaded pictures.</li>
<li>Show notes on single page, front page, archive page and etc.</li>
<li>Notes synced with WordPress commenting system but there’s option to turn it off.</li>
<li>Gravatar in the notes.</li>
<li>Commentator’s name in the notes.</li>
<li>Image thumbnail appear at comment area, but there’s option to turn it off.</li>
<li>No hard coding required.</li>
<li>Admin page.</li>
<li>Remove all database if you wish to not using the plugin anymore.</li>
</ol>

Guan Image Notes

Image tagging system sync with WordPress comment system. Or also known as image notes, or image annotation.

Mark

Adds a simple ‘Post-it’ widget to the Dashboard that allows you to leave yourself or other authors a note. The plugin can be configured and moved around as any other Dashboard widget. It will accept plain text or (sanitized) HTML. Only users with the capability “Edit dashboard” can edit the note.
This simple plugin is based on code from <a href="http://wpengineer.com/add-wordpress-dashboard-widgets/" title="Add WordPress Dashboard widgets" rel="nofollow ugc">WP Engineer</a> and <a href="http://rick.jinlabs.com/2009/02/01/how-add-options-to-your-wordpress-27-dashboard-widgets/" title="How to add options to your WordPress 2.7 Dashboard widgets" rel="nofollow ugc">Ricardo González Castro</a>. Leave your comments <a href="http://ideophone.org/dashboard-post-it/" title="Dashboard Post-it homepage" rel="nofollow ugc">here</a>.
Warning Your notes will be replaced by boilerplate text upon upgrading. Make sure to copy the content somewhere else before you upgrade and then paste it into the new version. Sorry about that!

Dashboard Post-it

Adds a simple 'Post-it' widget to the Dashboard that allows you to leave yourself or other authors a note.

Guan Image Notes vs Dashboard Post-it