Joe Dolson

Adds a custom field to your post editing screens to add custom styles applied only on that page or post.
Attach custom styles to any page, post, or custom post type. Separate styles can be attached for print, screen, or mobile. You can also store your own library of frequently-used styles.
How to use the style library:
<ol>
<li>Add the styles you want on your settings page.</li>
<li>Navigate to an article which requires specific styles.</li>
<li>Select the library style from the drop down, leaving the style textarea blank.</li>
<li>Update or post the new document.</li>
</ol>
A newly-selected style from the style library will always overwrite any previous hand-written styles. If you wish to alter the library styles for a specific page, you can do this in the textarea after you’ve saved the page with the style library template.
By default, editing your saved stylesheets will have no impact on previously saved post-specific styles; set the option to pull styles from the library to change this.
Note: custom styles will not be included on archive pages; only on single post/Page views.
The use you’ll get out of this plugin depends on the flexibility of the theme you’re using and your own knowledge of CSS (Cascading Style Sheets).

WP Post Styling

Define custom styles for any post, page, or custom post type. Example: journal-style publications which want to create a unique design for articles.

esthertyler

Transfered to new dev: https://profiles.wordpress.org/esthertyler
Maked by Esther Tyler: http://mycustomcss.com/
With this plugin you can put custom css code without edit your theme and/or your plugins (really useful in case of any theme/plugin update).
It contain also <a href="https://ace.c9.io/" rel="nofollow ugc">Ace (Ajax.org Cloud9 Editor)</a> Code Editor for write a good css code.
You can see in action (source code) here: <a href="http://www.vegamami.it/" rel="nofollow ugc">VegAmami</a> 🙂
PS: support file backup and – very important – static css file (fantastic for performance) 😉
<h4>Links</h4>
<ul>
<li>New dev: https://profiles.wordpress.org/esthertyler</li>
<li>Author Homepage: <a href="http://mycustomcss.com/" rel="nofollow ugc">Esther Tyler</a></li>
<li>Plugin maked for (demo link): <a href="http://www.vegamami.it/" rel="nofollow ugc">VegAmami</a></li>
<li>Ace (Ajax.org Cloud9 Editor): <a href="https://ace.c9.io/" rel="nofollow ugc">Ace (Ajax.org Cloud9 Editor)</a></li>
</ul>
<h4>Language</h4>
<ul>
<li>English</li>
<li>Italian</li>
<li>Full translatable!</li>
</ul>

My Custom CSS PHP & ADS

Enable to add Custom CSS Code via admin panel with Ace (Ajax.org Cloud9 Editor) + backup (see screen) and static file cache (best performance) :)

WP Post Styling vs My Custom CSS PHP & ADS