Change your blog's language based on the user's preferred language.
In Their Language detects the user's browser language preferences and attempts to switch your site/blog to that language.
One great example usage of this plugin is if your site/blog is managed by multiple people who speak multiple languages, then this plugin will automatically switch the administration area to each user's language.
Only translatable strings will be affected and only if a translation file is present for that language. See the Installation and FAQ tabs for more details on that.