<p><a href="http://pjdietz.com/wordpress-plugins/custom-css-js/" rel="nofollow ugc">Custom CSS and JS</a> allows you to add stylesheets and JavaScripts to any individual post by adding custom fields. Both CSS and scripts can be either internal or external. Since this is a plugin, the custom CSS and JavaScript are available to any theme used to display the post, as long as the themes call “wp_head”.</p>
<h3>Using the Plugin</h3>
<p>To use the plugin, add any combination of the following custom fields to your post.</p>
<p><strong>custom_css</strong><br />
Add an external stylesheet by adding a custom field with the name <strong>custom_css</strong>. The value of the field should be the path to your css file.</p>
<p><strong>cusrom_css_code</strong><br />
Add an internal stylesheet by adding a custom field with the name <strong>custom_css_code</strong>. Include your CSS code as the value. (Do not include the style tags.)</p>
<p><strong>custom_js</strong><br />
Add an external JavaScript by adding a custom field with the name <strong>custom_js</strong>. The value of the field should be the path to your script.</p>
<p><strong>custom_js_code</strong><br />
Add an internal JavaScript by adding a custom field with the name <strong>custom_js_code</strong>. Include your JavaScript code as the value. (Do not include the script tags.)</p>
<h3>Custom Fields Order</h3>
<ol>
<li>The external styles and scripts are included before the internal ones.</li>
<li>If you include multiple entries for a given field, the entries will be included in order.</li>
</ol>
<h3>Okay, but what if I don’t like those tags?</h3>
<p>Just edit custom-css-js.php and change the constants defined near the top of the file.</p>
<h3>Note</h3>
<p>This plugin only works with individual posts and pages. It does not work for list pages (e.g., the index page, search results).</p>


Custom CSS and JS

Custom CSS and JavaScript allows you to add custom internal and external CSS and JavaScripts to individual posts.

vgstef

<p>Sometimes, we just want to offer visitors simple variations of our website theme. Sometimes, we simply want to offer a stylesheet with improved accessbility. There are plugins that let you choose a different theme, but this plugin offers you to change only the stylesheet. In the admin settings, you can configure as many different stylesheets as you want. Those possibilities are offered in a list on the front page.</p>
<p>The list of available stylesheets can be shown in a dropdown list or as a series of icons. It can be shown using the widget or in a page/post using the shortcode, or directly in the template using the php function.</p>
<p>On the frontend, when a choice is made in the dropdown list, the webpage is reloaded using the chosen stylesheet.</p>
<h4>Plugin Features</h4>
<ul>
<li>Easy installation/setup</li>
<li>Any number of switchers</li>
<li>Each switcher can have any number of stylesheet options</li>
<li>Set a default stylesheet</li>
<li>Multiple instances of switchers/stylesheet lists can be present on the same page.</li>
<li>Choice between a dropdown or icon list for each list</li>
<li>Can be used with a shortcode in a post/page, with the widget and with a php function in the theme</li>
<li>For each list, possibility to show/hide the title</li>
<li>Optional single switcher button (text or icon)</li>
<li>Chose between theme relative path or absolute path (useful to customize multisite)</li>
<li>Optional automatic theme rotation (weekday, week, month, year or random)</li>
<li>Ready for internationalization</li>
<li>Complete uninstall (removes options and widgets)</li>
</ul>
<h4>Languages already available</h4>
<ul>
<li>English</li>
<li>French</li>
<li>Spanish (thanks to Andrew Kurtis from WebHostingHub)</li>
<li>Serbo-Croatian (thanks to Andrijana Nikolic from WebHostingGeeks)</li>
</ul>
<p>To see an example, visit <a href="http://web.globulesverts.org/wp-user-stylesheet-switcher" rel="nofollow ugc">plugin page</a>.</p>


WP User Stylesheet Switcher

I'm using this on a site I'm developing that will have a "feminine style" and a "masculine style".  The site is in development so I didn't want to replace the default style.css as that would mean updating two stylesheets (ugh!).  Because the style switcher is loaded in the header after the main stylesheet, this is  what I did to cut down work ...

In the plugin I identified the default stylesheet as "Feminine Style" and entered a fake stylesheet name so it would never get replaced.  I then created a real "Masculine Style" and entered it's correct stylesheet name.  

This way the masculine overrides just the feminine styles I add to it to change :D  It works great.

Works Great

Adds a list (or multiple list) of stylesheets in the frontend to allow visitors to choose a different visual look for the website.

Custom CSS and JS vs WP User Stylesheet Switcher