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.

Andrea Porotti

Using this plugin you can attach notes to some elements in the WordPress dashboard, such as:
<ul>
<li>posts</li>
<li>pages</li>
<li>custom post types from other plugins (except the notes from this plugin)</li>
<li>users</li>
<li>plugins</li>
<li>dashboard sections</li>
<li>the whole dashboard</li>
</ul>
It can be helpfull if you manage a site with other people or just to take notes for yourself.
Features
<ul>
<li>manage notes like the standard posts by opening the Notes page from the admin menu.</li>
<li>while editing a note, use the meta box on the right to set note properties (position, color,…)</li>
<li>manage section and global notes from the admin bar.</li>
<li>manage item notes (eg. posts and pages) from the custom column in the admin pages.</li>
<li>get notes details by hovering the mouse on the “Info” links or clicking on the “I” icons.</li>
<li>add text, images and links in the note content.</li>
<li>deleted notes go to the trash, so they can be restored.</li>
<li>automatically discovers custom post types added by other plugins (eg. events, books…).</li>
<li>creates a list of the dashboard sections based on the admin menu items.</li>
</ul>
Configuration
Settings for the plugin are available on the Settings -> JAMP Notes page.
Please note:
<ul>
<li>by default the plugin data is kept after uninstall. You can choose to delete notes and settings enabling the data removal option.</li>
<li>after activation, the plugin enables notes for all the existing public post types. If you then install other plugins which create new post types, you have to manually enable them in the JAMP settings.</li>
</ul>
Permissions
The notes are currently available only for the users with the “Administrator” role. 
Each Administrator can manage all notes.
Support
If you find any errors or compatibility issues with other plugins, please let me know in the support forum. Thanks!
Privacy
This plugin does not collect or store any user data. It does not set any cookies and it does not connect to any third-party services.

JAMP Notes (Just Another Memo Plugin)

This plugin allows you to attach notes to some WordPress elements like posts, pages, dashboard sections and more.

Guan Image Notes vs JAMP Notes (Just Another Memo Plugin)