Il Portale della Lingua Italiana - The website of the Italian Language developed by the Ministry of Foreign Affairs and International Cooperation

Interesting Articles:

Liberi di volare - Arabismi nella lingua italiana: scopriamo quanti ne usiamo ogni giorno

Online Excercises

Rai Cultura Italiano - The portal for learning Italian by RAI, the national public broadcasting company of Italy

Io Parlo Italiano - An online learning program by RAI Educational

Alma TV - A web tv dedicated to Italian culture and language by Alma Edizioni

Italiano per Stranieri - Resources on Italian grammar and more by Loescher Editore

Campus Italiano per stranieri - Exercises on grammar and vocabulary by Mondadori Education 

Zanichelli Benvenuti - Exercises with dialogues, Flash Player needed 

BBC Languages Italian - Many different resources on Italian, including a list of Italian media

Eserciziario Online - Practice with these exercises by UofT

Radio Arlecchino - Train your listening skills with this podcast, includes transcripts 

Prova il Tuo Italiano - Test your Italian level with this website

Dictionaries, Encyclopedia, Books, and Audiobooks

L'Italiano in Famiglia -  A series of videos and exercises on everyday language 

Vocabolario Treccani Online - A free Italian dictionary 

Enciclopedia Treccani Online - One of the most famous Italian encyclopedia 

Dizionario De Agostini - An Italian dictionary, plus Italian-English dictionary by De Agostini 

Dizionario Garzanti online - Another dictionary with translation function by Garzanti

Liber Liber Libri A vast collection of free Italian ebooks

Liber Liber Audiolibri A great selection of free Italian audiobooks

TV and Radio

RaiPlay - Access to all Rai channels and shows in streaming and on-demand (free registration needed)

RaiPlay Radio Access to all Rai Radio channels live or on demand 

Radio Italia - Italian music 24/7