This plug-in automatically detects your visitor's language and uses it instead of the site's default language.  That way, your site is automatically translated, whether users are logged in or not. You need to have language packs installed for this plug-in to translate your site.

NOTE: This plug-in requires you to make changes to a core file, languages.php.  You will need to replace engine/lib/languages.php with the languages.php file provided.  The reason behind this is that Elgg 1.5 loads plug-ins after it has already loaded the login page, index page and other core components.  By the time this plug-in is loaded, those pages have already been created in the site's default language, so they can no longer be translated.  But don't worry -- the changes made are not specific to my plug-in, in the hope that they can make it into the next Elgg release.

To see this plug-in in action, visit http://oakpages.com.  Then, change the language in your browser's preferences and refresh the page.  OakPages.com will now be presented in the language you just selected!