Most Spanish don't use translation tools, but for those people who work in translation, then the websites suggested by Diego are both very good resources (not only for Spaniards, but for other nationalities too).

Hi there! I've meet some translators and as far as I know they were using sites like; http://www.wordreference.com/es/ ---> for any language www.rae.es ---> official Spanish dictionary and checking in forums around the internet. There seems to be a huge community that discuss language peculiarities in private open forums so maybe it won't be a bad idea to check around and become a member of some of them. bye bye!