dwieeb

With this plugin, you will be able to include certain CSS or JS files in only selected posts, pages, or other post types, instead of including them everywhere. You can also edit inline CSS & JS and include CSS & JS files from anywhere on specific posts and pages.
It places meta boxes in the WordPress post editor so it’s easy to select which files you want to include with the post you’re currently editing. This plugin works well for all websites, large and small, and it works well with WordPress multi-site (WordPress MU). Tested up to 3.1 beta 2.
See this plugin’s <a href="http://www.danielimhoff.com/wordpress-plugins/specific-files/" rel="nofollow ugc">page</a> on my website for information/comments/questions. I am open to the idea of suggestions and patches to this plugin! If you enjoyed this plugin, please <a href="http://www.danielimhoff.com/donations/" rel="nofollow ugc">donate</a> or <a href="http://www.danielimhoff.com/donations/" rel="nofollow ugc">say thanks</a>.
Todo:
<ul>
<li>Add a “remove references” button on the options page so people can remove file references without having to delete the file.</li>
</ul>

Specific Files

This plugin allows you to include CSS or JS files in specific posts and pages.

thom4

fabrizim

<a href="http://lesscss.org" rel="nofollow ugc">LESS</a> is a templating language based on top of CSS. It provides numerous enhancements to speed up development and make its maintenance easier.
Theme developers can even bundle the plugin without worrying about conflicts: just include the special <code>bootstrap-for-theme.php</code> and read its instructions.
<h4>Features</h4>
<ul>
<li>Variables</li>
<li>Mixins (inheritance of rules)</li>
<li>Nested Rules (write less, do more)</li>
<li>Accessors (inherit a value from a specific rule)</li>
<li>Functions (logic operations for dynamic results)</li>
</ul>
The plugin lets you concentrate on what you need: coding CSS. Everything else is handled automatically, from cache management to user delivery. 
Seriously.
<h4>Documentation</h4>
Advanced topics on how to use the plugin API are <a href="https://github.com/oncletom/wp-less/tree/master/doc" rel="nofollow ugc">available on the Github project documentation</a>.
<h4>Requirements</h4>
The sole requirement is to use WordPress API and LESS convention: the <code>.less</code> extension.
Minimal Requirements: PHP 5.3 and WordPress 3.2. 
Relies on: <a href="http://lessphp.gpeasy.com/" rel="nofollow ugc">Less.php</a>, <a href="https://wordpress.org/extend/plugins/plugin-toolkit/" rel="ugc">plugin-toolkit</a>.
Notice: in case you’d like to drop the usage of this plugin, it’s safe to do it. You will just need to convert back your stylesheets to CSS.

WP-LESS

Implementation of LESS (Leaner CSS) in order to make themes development easier.

Specific Files vs WP-LESS