scribu

This plugin improves the gallery template by making the following tweaks:
<ol>
<li>Puts all the gallery css in a separte file, for easy customisation and faster page load.</li>
<li>Adds an id attribute to the code, so that two or more galleries can have a different number of columns and still display correctly on the same page.</li>
</ol>
Links: <a href="http://scribu.net/wordpress/improved-gallery" rel="nofollow ugc">Plugin News</a> | <a href="http://scribu.net" rel="nofollow ugc">Author’s Site</a>

Improved Gallery

Improves the built-in gallery in WordPress 2.5 and newer.

mabujo

Modern browsers allow pages to prefetch DNS records of external libraries. This plugin looks through WordPress enqueued scripts and styles and adds DNS prefetch statements for scripts and stylesheets added by other plugins.
This means that when the browser comes to download an external script or stylesheet, it already has looked up the DNS record for the external domain, and can proceed immediately to downloading the script, saving latency during loading of external resources.
You can read more about this technique in the <a href="https://www.chromium.org/developers/design-documents/dns-prefetching" rel="nofollow ugc">Chromium document</a>.
Plugin page <a href="https://mabujo.com/blog/automatic-dns-prefetch-wordpress-plugin/" rel="nofollow ugc">Automatic DNS Prefetch plugin @ mabujo</a>.

Automatic DNS Prefetch

Works as advertised

This plugin speeds up your page load speed by adding DNS prefetch statements for external libraries.

Improved Gallery vs Automatic DNS Prefetch