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.

Creativemotion

Alexander Kovalev

webcraftic

Transliteration is the transformation of one character into another, for example Cyrillic characters, into Latin. Usually transliteration is used to improve the readability of permalinks and avoid problems with displaying and reading files, because everything in network based on the Latin alphabet. Many plugins made by English-speaking developers do not optimize under the Cyrillic alphabet and can work unstable.
Cyrlitera transliteration plugin replaces Cyrillic, Georgian characters at posts, pages and tags to create readable permalinks. Also this plugin fixes incorrect file names and removes unnecessary characters, which can cause problems when accessing this file.
Cyrillic link example: 
_site.dev/%D0%BF%D1%80%D0%B8%D0%B2%D0%B5%D1%82-%D0%BC%D0%B8%D1%80
Converted into the Latin alphabet: 
_site.dev/privet-mir
In the first case, you can not visually understand the text of encoded link. In the second case, the link transliteration is implemented, everything looks more clear and the link is more shorter.
An example of incorrect filename transliteration: 
%D0%BC%D0%BE%D0%B5_image_ 290.jpg 
A+nice+picture.png
Images transliteration example: 
moe_image_ 290.jpg 
a-nice-picture.png
If you ignore file names creation rules, then you can get 404 errors and broken links.
Therefore, create file names using Latin characters and numbers, avoiding special characters, except dashes and underscores. Alternatively, use this plugin. It will do all this work automatically when uploading a file via the WordPress interface and reduce the number of broken links.
<h4>FEATURES</h4>
<ul>
<li>
Converts permalinks of existing posts, pages, categories and tags when options are enable;
</li>
<li>
Keeps the integrity of records’ and pages’ permalinks;
</li>
<li>
Creates a redirect from old posts and pages names to the new ones with converted links;
</li>
<li>
Performs transliteration of the attachments file names;
</li>
<li>
Converts filenames into lowercase;
</li>
<li>
Includes Russian, Belarusian, Ukrainian, Bulgarian, Georgian symbols;
</li>
<li>
You can advance a characters base for transliteration;
</li>
<li>
You can roll back changes if the plugin converted your URLs incorrectly.
</li>
</ul>
<h4>THANKS TO THE PLUGINS’ AUTHORS</h4>
We used some plugins functions: 
WP Translitera, Rus-To-Lat, Cyr to Lat, Clearfy — WordPress optimization plugin and disable ultimate tweaker,translit-it, Cyr to Lat enhanced, Cyr-And-Lat, Rus filename translit, rus to lat advanced
<h4>RECOMMENDED SEPARATE MODULES</h4>
We invite you to check out a few other related free plugins that our team has also produced that you may find especially useful:
<ul>
<li><a href="https://wordpress.org/plugins/clearfy/" rel="ugc">Clearfy – WordPress optimization plugin and disable ultimate tweaker</a></li>
<li><a href="https://wordpress.org/plugins/comments-plus/" rel="ugc">Disable Comments for Any Post Types (Remove Comments)</a></li>
<li><a href="https://wordpress.org/plugins/webcraftic-updates-manager/" rel="ugc">Disable updates, Disable automatic updates, Updates manager</a></li>
<li><a href="https://wordpress.org/plugins/cyr-and-lat/" title="Cyr-to-lat reloaded" rel="ugc">Cyr-to-lat reloaded – transliteration of links and file names</a></li>
<li><a href="https://wordpress.org/plugins/disable-admin-notices/" title="Disable admin notices individually" rel="ugc">Disable admin notices individually</a></li>
<li><a href="https://wordpress.org/plugins/gonzales/" title="WordPress Assets manager, dequeue scripts, dequeue styles" rel="ugc">WordPress Assets manager, dequeue scripts, dequeue styles</a></li>
<li><a href="https://wordpress.org/plugins/hide-login-page/" title="Hide login page" rel="ugc">Hide login page</a></li>
</ul>

Cyrlitera – transliteration of links and file names

The plugin converts Cyrillic, Georgian links, filenames into Latin. It is necessary for correct work of WordPress plugins and improve links readabilit …

Bunny’s Language Linker vs Cyrlitera – transliteration of links and file names