Ryan

Easily add custom JavaScript or CSS to a single post or page.
When activated, a new icon is added to the post edit page near the icon you use 
to add media to a post. Clicking the new icon brings up a screen where you can 
insert JavaScript and CSS that will be included with the current post.
Anything entered into the text field on the JavaScript tab will be inserted into 
the <head> section of your web page. Same is true of the CSS tab. This allows 
you to insert arbitrary JavaScript and CSS into any post or page you would 
like without having to resort to loading it on all pages.

Insert JavaScript and CSS

Adds fields to the post and page edit pages that allow you to insert custom JavaScript or CSS for that post or page.

Kevin Newman

WraithKenny

This plugin allows Admin users the ability to add custom CSS and JavaScript directly into individual Post, Pages or any other registered custom post types. You can also add classes to the body tag and the post container. There is a Global settings page for which you can write Scripts n Styles for the entire blog.
Admin’s can also add classes to the TinyMCE “Formats” dropdown which users can use to style posts and pages directly. As of Scripts n Styles 3+ styles are reflected in the post editor.
Because only well trusted users should ever be allowed to insert JavaScript directly into the pages of your site, this plugin restricts usage to admin type users. Admin’s have access to even more sensitive areas by definition, so that should be relatively safe 😉
<h4>Notes about the implementation:</h4>
<ul>
<li>Admin users, or more specifically, any user with the <code>manage_options</code> and <code>unfiltered_html</code> capabilities (which by default is only the admin type user) can use this plugin’s functionality. Some plugins extend user rolls, and so this plugin would naturally extend include rolls that have the appropriate capability.</li>
<li>CSS Styles are embeded, not linked, at the bottom of the <code>head</code> element with <code>style</code> tags by using <code>wp-head</code>. If your theme doesn’t have this hook, this plugin (as well as most others) won’t work.</li>
<li>JavaScript is embeded, not linked, at the bottom of the <code>body</code> (or <code>head</code>) element with <code>script</code> tags by using <code>wp-footer</code> (or <code>wp-head</code>). If your theme doesn’t have this hook, this plugin (as well as most others) won’t work.</li>
<li>There is no input validation. This plugin puts exactly what you type in the meta box directly into the <code>html</code> with no error checking. You are an Admin, and we trust you to be carefull. Try not to break anything.</li>
<li>Do to the licensing of the libraries used, this plugin is released “GPL 3.0 or later” if you care about those things.</li>
</ul>

Scripts n Styles

This plugin is simply awesome. 
No other words to say. 

Must have! Great Job.

This plugin allows Admin users to individually add HTML, custom CSS, Classes and JavaScript directly to Post, Pages or any other custom post types.

Insert JavaScript and CSS vs Scripts n Styles