macbre

This extension has been inspired by http://devel.kostdoktorn.se/cache-translation-object and gives up to 5x speed increase when using WordPress with “custom” (i.e. non English) localisation files.
MO object created by WordPress is cached and stored in the <code>/wp-content/cache/</code> directory and then used when loading localisations.

l10n cache

Improves site performance by providing caching for localisation objects (*.mo files).

jstar198

Adds an extra panel to the post/page edit page which allows you to enter the META keywords & description for that page in each enabled language. Also adds an optional browser title override (does not affect post title).
Note 1: This plugin requires that <a href="http://www.qianqin.de/qtranslate/" rel="nofollow ugc">qTranslate</a> is installed and activated.
Note 2: This plugin does not work well with <a href="https://wordpress.org/extend/plugins/all-in-one-seo-pack/" rel="ugc">All In One SEO</a> and potentially any other plugin or theme which tries to set your META tags.
<h4>Thanks</h4>
I’d like to thank the following people for their contributions (in chronological order):
<ul>
<li>Victor Berchet — Help with initial localisation; French translation</li>
<li>Benoit Gauthier — autosave bug fix</li>
<li>Filippo Pisano — Italian translation</li>
<li><a href="http://pc.de/" rel="nofollow ugc">Marcis G.</a> — Belorussian translation</li>
<li>Almaz — Russian translation</li>
<li><a href="http://www.heftrucknederland.nl/" rel="nofollow ugc">Renate Kramer</a> — German translation</li>
<li><a href="http://wpwebshop.com/blog/" rel="nofollow ugc">Rene</a> — Dutch translation</li>
<li>banane — Bugs with WordPress 3 compatability.</li>
<li>Alexander of <a href="http://webhostinggeeks.com/" rel="nofollow ugc">Web Hosting Geeks</a> — Romanian translation</li>
<li>Branco Radenovich of <a href="http://webhostingw.com/" rel="nofollow ugc">Web Hosting Watch</a> — Slovakian translation</li>
</ul>

qTranslate META

For users of qTranslate, allows you to set multi-lingual META tags and a <title> override for your posts and pages.

l10n cache vs qTranslate META