I have already written about (im)possible translation on this blog. The series on Genette's Mimologiques (first part here) is also relevant, because Cratylism has strong implications for the theoretical possibility of translation. At some point, I should write something about Steiner's After Babel.
Lately, I've been looking through the monumental Dictionary of Untranslatables: A Philosophical Lexicon. On a lighter note, here are some illustrated examples of hard to translate concepts from several languages. Both sources discuss the term saudade.
P.S. As I'm writing this post, I'm also reading a comment on Slashdot about the different meaning of "government" in British vs. American English...