Aaron Edwards

Tired of your custom plugin and theme translation files getting wiped out every time you use the WordPress auto-updater? Install and activate this plugin and 
WordPress will look for missing translation files in the WP_LANG_DIR where you keep your WordPress translation files.
<h4>UPDATE</h4>
In WordPress 3.8 and greater this plugin’s functionality is included in core. You can put translation files in: 
* Plugins: /wp-content/languages/plugins/textdomain-locale.mo 
* Themes: /wp-content/languages/themes/textdomain-locale.mo
A free plugin by Aaron Edwards of <a href="http://uglyrobot.com/" rel="nofollow ugc">UglyRobot Web Development</a>.

Translation Preserver

A simple plugin that helps preserve your custom plugin translations through auto-updates by allowing you to put them in your WP languages folder.

nevis2us

<ul>
<li>Allows to translate your website content to many languages.</li>
<li>Includes a sidebar widget with flags.</li>
<li>Includes a shortcode for better control of widget placement and styles.</li>
<li>Includes required attribution.</li>
<li>Allows to translate login page and administration panel.</li>
<li>Has basic support for RTL languages.</li>
<li>Triggers a custom event after the page has been translated.</li>
<li>Sets WordPress locale to the selected language.</li>
<li>Loads external scripts asynchronously.</li>
</ul>
<a href="http://ipros24.ru/wordpress/" rel="nofollow ugc">Demo</a> 
<a href="http://corde.ipros24.ru/" rel="nofollow ugc">Demo 2</a>
Since version 1.11 external scripts are loaded asynchronously, so when Google services are not responsive this won’t delay loading your site. 
Since version 1.12.2, for security reasons, external scripts won’t be loaded if the user is logged into an administrative account. This means the translation won’t work until the user logs out.
Plugin and theme developers can hook to a custom event to perform some actions after the page has been translated. This can be used e.g. to adjust element styles and positioning.
Changing WordPress locale allows you to use already installed language files and flip the site content in RTL languages. This feature can also be used by developers to quick check translations and view site layout in RTL. Sometimes it may be necessary to reload the page to set the locale. You can turn this on in the plugin settings.
<a href="http://ipros24.ru/ipros24-google-translate-advanced-usage-and-examples/" rel="nofollow ugc">Advanced usage and examples</a>
Other iPROS24 plugins
<a href="https://wordpress.org/plugins/ipros24-notices/" rel="ugc">iPROS24 Notices</a>

Translation Preserver vs iPROS24 Google Translate widget