Rosetta Stone of the 21st Century?
You can rip the subtitle information out of VOB files (that are on DVDs). Not only will you be able to search for "Never get involved in a land war in Asia" but how to say it in Spainish and other languages.
I think (and I might be wrong here) that DVD subtitle information would provide the biggest human repository of translation information.
Page of subtitle software:
No doubt this is copy protected (and copyrighted) though. But it would probably be fair use to hold this in a peer-to-peer fashion. You only hold and index the DVDs you own. Then just return the results of the search.
Now if we combine it with the graphical search engines (Eikon or eVision or something) you can put in a picture of an actress/actor and get all the movies they appear in.
This probably isn't a million miles away from my video store project that I did in High School. :-)