Steph

This plugin assumes you have a site in two or more languages, and that you are using a separate WordPress install for each language. It helps you create links between the same pages in different 
language versions.
You should have a pattern of parallel sites with urls like http://stephanie-booth.com/en/, http://stephanie-booth.com/de/, http://stephanie-booth.com/fr/. Maybe the page 
http://stephanie-booth.com/en/about is equivalent to the page http://stephanie-booth.com/fr/a-propos. The plugin adds a DBX box in the edit/create page admin form, named “Other Language Slugs”. In 
this case, you’d edit the “about” page, and paste the fr slug (“a-propos”) in the appropriate field.
The plugin will then display a small link to the page in the other language at the bottom of your page, or in your menu bar if you’re using a Sandbox-based theme.
Careful! This only works for Pages, not posts!
For intelligent user redirection when they land on the home page, you might want to try using the technique described here: http://climbtothestars.org/archives/2007/12/28/browser-language-detection-and-redirection/
<h3>Future Development</h3>
Here’s what I’d like this plugin to do, someday:
<ul>
<li>automatically capture URLs like http://stephanie-booth.com/en/a-propos and redirect them to http://stephanie-booth.com/en/about (that’s what happens when people edit URLs directly, just replacing 
the language code — I do it all the time)</li>
</ul>

Bunny’s Language Linker

Helps you create links between equivalent (but different language) pages between WordPress installations.

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.

Bunny’s Language Linker vs qTranslate META