I just learned that Google Spreadsheets has added a new function: GoogleTranslate(text,from,to). It works just as you would expect, allowing you to translate from among dozens(?) of languages. While I'm not sure yet how I'd use this feature, I have a hunch it'll be really useful.
Here's a toy example:
Other possibilities: Mix the admin interface idea with translations, to automate the creation of multi-lingual apps; store text on sheet, the translation on another, and create a sort of basic flashcard system.