Best Poster EverWell, maybe not. I had a poster in college that was a cutaway of the USS Enterprise (NCC-1701A) from Star Trek: The Motion Picture that...oh, never mind.
Anyway, this one came to me by email, and I'm sorry that I can't give credit where credit is due. Apparently it's an internal "loose lips sink ships" poster from Lockheed Martin about the dangers of espionage. Love the booze bottles holding the corners, particularly the Napoleon V.S.O.P.
I've also posted a larger version of it here.
UPDATE: I've fixed the link to the Webshots gallery.