COES: Herramienta Lingüística de Libre Distribución para la Lengua Española - Set of data files that implements a Spanish (castellano) dictionary with 52,000 roots (approx.) and their derivated forms. Includes Spanish spelling dictionary. Based on Unix tool ispell. Distributed under GNU "General Public License of the Free Software Foundation".
English<->Spanish online dictionary - 60,000 entries. Wildcards accepted. Definition brings up links to each word in definition but not necessarily all in dictionary. System by Gleb Beliakov.
MLIS DicoPro project - Online dictionary consultation for translation professionals in an Intranet environment. User survey questionnaire for language professionals.
OECD Macrothesaurus - Access to the four versions. English French Spanish German.