Dictionaries, glossaries and other resources
MERRIAM-WEBSTER
http://www.merriam-webster.com

Dictionaries, glossaries and other resources
WORDMAGIC
http://www.wordmagicsoft.com/diccionario

Dictionaries, glossaries and other resources
IATE
http://iate.europa.eu/

Dictionaries, glossaries and other resources
BABYLON DICTIONARIES
http://www.babylon.com/free-dictionaries

Spanish language resources
Dictionary of the Royal Spanish Academy
http://www.rae.es/recursos/diccionarios/drae