I use Nice Translator to translate back and forth between English and Spanish. I had been using Google translator before, but having to translate both English and Spanish was too much of a hassle using Google. Nice Translator has good, sometimes better, grammar and structure, but the best part is that it does simultaneous translation. All I need to do is type whatever I want translated, and it does it in Spanish and English. It also comes in a variety of other languages - Arabic, Vietnamese (useful for communicating with my parents), Lithuanian, Korean, etc. The only issue is that the text box is too small and can sometimes be frustrating when you want to edit something you've typed.