Terminology databases:

EURADICAUTOM
http://ec.europa.eu/eurodicautom/Controller
Terminology databases containing technical and scientific terms in all languages of the European Union.

IATE - UE
https://iate.cdt.eu.int/iatenew/login.jsp

EUROVOC
http://europa.eu/eurovoc/
European Union Thesaurus

ILOTERM
http://www.ilo.org/iloterm/ns?a=T_P1.start&u=&login=USER&password=isiterm&direct=YES#expanded
Terminology database of the International Labour Office.

General monolingual and bilingual dictionaries

Italian

Dizionario della lingua italiana Treccani
http://www.treccani.it/site/lingua_linguaggi/consultazione.htm

Dizionario Italiano De Mauro Paravia ondine
http://www.demauroparavia.it/lemmario

Spanish

RAE
http://www.rae.es/
Diccionario de la lengua española. 22° Edición

CLAVE
http://clave.librosvivos.net/
Diccionario en línea del español actual

English

Onelook
www.onlook.com
These are very good because they carry out multiple searches of online dictionaries and also suggest possible translations and definitions of terms.

Merrian-Webster Collegiate Dictionary
http://www.m-w.com/

Webster online dictionary – Rossetta’s Edition
http://www.websters-online-dictionary.org/
Dictionaries useful for ‘cross searches’

Wordreference
Online French, Italian and Spanish Dictionaries
www.wordreference.com