Here are some sites for translating words. 

A WORD OF CAUTION: These dictionaries do not think, therefore, a word may be translated, but it probably won't translate a phrase or sentence correctly even if it says it does. Sometimes there are cultural differences, sintax difference, idioms, expressions that make it difficult to translate back and forth.

This first one is my favorite:

WORD REFERENCE
Free online translation dictionaries for English, Spanish, French, and Italian. Also includes a verb conjugator, a phrase context list, and forums where many questions have already been answered by native speakers. You do not have to join to make use of resources. Joining just allows you to post. 
http://www.wordreference.com/

WEB WORKBOOKS DICTIONARY
Spanish dictionary with 120,000 entries and 45,000 voice files: http://www.webworkbooks.com/spanish/dictionary/resultenglish.php?palabra=saber

YAHOO SPANISH
Yahoo Spanish English Dictionary
http://education.yahoo.com/reference/dict_en_es/

FREE DICTIONARY
(contains many languages)
http://www.freedict.com/onldict/spa.html

TRAVEL DICTIONARY
http://dictionaries.travlang.com/SpanishEnglish/

FREE TRANSLATOR
http://www.freetranslation.com/

SPANISH DICTIONARY
http://www.spanishdict.com/

LEGAL DICTIONARY (English-Spanish)
www.ernestoromero.net/LS.pdf

REGIONAL SPANISH DICTIONARY (Mexico)

http://www.webconferencia.net/directorio/detail/9189/diccionario-breve-de-mexicanismos.html