Kashiv

This plugin allows to have admin panel in different language (for example, admin’s native language) from blog’s home language. This is useful when you have blog in e.g. german but you want to have admin panel in english.
This plugin works simply. It adds a “Language” form element in user profile.
It works in Dashboard as well as on the blog’s homepage.

Admin Language

This plugin allows to have admin panel in different language (for example, admin's native language) from blog's home language.

Alex Zappa

The lang attribute specifies the language of the element’s content. 
Common examples are “en” for English, “es” for Spanish, “fr” for French, and so on. 
This plugin slice the language attribute for HTML tag, For example: lang=”en-US” to lang=”en”

HTML Global lang Attribute

This plugin slice the language attribute for HTML tag, For example: lang="en-US" to lang="en"

Admin Language vs HTML Global lang Attribute