Babelfish Translation Service: Proof that machines still can't translate poetry
Dizionario Collins: Among the best online dictionaries; quite user-friendly
Dizionari e glossari: retorica, stilistica, metrica, ecc.
Artemotore.com: An Italian vocabulary of film terms
Garzanti: Easily the best online Italian dictionary. You have to register, but it's free and very user friendly.
ForeignWord.com: Rather good and user-friendly
Cinematografo.it: An exceptionally useful Italian/English, English/Italian dictionary of film terms
The Logos Dictionary: An amazing resource. Much, much more than a dictionary!
Girodivite.it: A dictionary of writers, scriptwriters, directors, and actors who have contributed to the development of world cinema.