Matthew Haines-Young

Minification & concatenation of JS and CSS files can reduce the file size of your assets, and reduce the number of HTTP requests, helping improve page load times.
The plugin takes a manually defined list of script/style handles, and minifies and concatenates them into a single file which is then cached for future use.
Features.
<ul>
<li>Minifies & concatenates scripts and styles loaded using the WordPress dependency enqueueing system.</li>
<li>Handles scripts loaded in the header & footer.</li>
<li>Complete control – only a manually defined list of files is processed.</li>
<li>Multiple, independently processed files.</li>
<li>Minified files are only loaded if at least one component file should be loaded.</li>
<li>Compatable with localized scripts.</li>
<li>Helper tool – displays a list of scripts and styles enqueued on each page on the front end of the site.</li>
</ul>

MinQueue

Minify & Concatenate Enqueued Scripts & Styles.

Clearfy Cache – WordPress optimization plugin, Minify HTML, CSS & JS, Defer vs MinQueue