I'm somewhat fluent in German and I'm currently learning Danish. I mainly translate songs into English.
"When the violin repeats what the piano has just played, it cannot make the same sounds and it can only approximate the same chords. It can, however, make recognisably the same 'music', the same air. But it can do so only when it is as faithful to the self-logic of the violin as it is to the self-logic of the piano." John Ciardi, Translator's Note in Dante's The Inferno
dict.cc: Mainly a German/English dictionary but several other languages are also available, as well as translations for idioms
Linguee: A dictionary which also displays bilingual parallel texts, making it very useful for looking up phrases and idioms
Den danske ordbog: A Danish dictionary which also lists some idioms