Seems like this has been up for a while, but I have never seen the Google Request for Volunteer Translators before. You can sign up quickly, all you need is a Google account. Lots of languages are a 100% complete, see the language status page for languages that remain to be translated. Even if a language is 100% translated, it is possible that they add more "messages to the Google interface" according to the FAQs. Of course to qualify, you must follow the style guide and agree to the "Legal Stuff" as they call it.
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