rufein

WordPress Seo Integration is a plugin to integrate the WordPress SEO plugin by Yoast plugin and mqTranslate (a fork of qtranslate) 
to manage the meta fields and sitemaps in a website with different languages.
The plugin is an Alpha version and only has the next features:
<ul>
<li>Administration panel to manage the meta fields filtered by language. The plugin make use of the WordPress SEO functions to measure the 
quality of SEO of every post in the website.></li>
<li>Build a sitemap with languages. the plugin build a sitemap from the type of post and from the language. For example, it builds an 
xml sitemap called page-es and other called page-en.</li>
</ul>
<h3>Arbitrary section</h3>

Integration of Yoast wordpress SEO module with mqtranslate module

Integration between the popular Wordpress SEO module by Yoast and mqtranslate plugin (a fork of qtranslate that is updated).

Guido Eugenio aka Zhenya

mqTranslate Separate Comments is a fork of the qTranslate separate comments plugin, extending the original software with collaborative and team-oriented features.
This plugin separates the user comments by the language they viewed the article, in this way you avoid duplicate content (which is frowned-upon from search engines) and comments in other languages than the one the current visitor is using (which is generally bad user experience).
You can manually change the language of each comment (and you will have to set it in the begining). 
Bulk-editing of the comments language is also available.
The plugin is using comment-meta to specify the language for each comment, so nothing will break if the plugin is deactivated.
It also should work out-of-the-box for all themes that use the <code>comments_template()</code> function to render their comments.
The plugin also fixes an issue of mqTranslate. The issue consists in the fact that whenever a user posts a comment (while viewing a post in a language different than the default one), he is redirected back to the post but in the default language and not the language he was reading the post before posting the comment.

mqTranslate Separate Comments

Automatically separates the user comments by the language they viewed in the article.

Integration of Yoast wordpress SEO module with mqtranslate module vs mqTranslate Separate Comments