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.

koopersmith

A simple custom CSS plugin for themes that integrates with the new theme customizer.
Warning: Do not use this plugin in an untrusted environment. This plugin currently does not sanitize the CSS.
At the moment, it’s really more a proof-of-concept and example than anything else.

A simple custom CSS plugin for themes that integrates with the new theme customizer.

WP Post Styling vs CSS