There is a large number of monolingual sites that, even though are not translated, provide outstanding resources for specialized translators or for the general public. Try Systran for fast English Spanish Translations. This company has worked with an excellent group of linguistics to create an excellent software that allows automatic English-Spanish translations. Be aware that while these automatic tools are very good and helpful, they should not be used to publish content without the supervision of a professional native speaker.
The National Association for Bilingual Education is the only national professional organization devoted to representing Bilingual Learners and Bilingual Education professionals.
The WordReference Dictionaries are one of the best resources for translations. They are not only outstanding dictionaries, but also an excellent source of information. Visit the forums when you do not find a particular definition. They are an excellent source of information you do not find in common books. We always recommend to have a rather critical attitude while taking the advice from forums and other non-authoritative sources.
Nothing beats an authoritative source of information such as the Real Academia Española-translated as Spanish Royal Academy. There are no ambiguities in the Spanish language. Everything is directed by the Royal Academy. This makes this specific language more rigid than English, but a translator has the advantage of a solid structure on which to stand.