The movie is #1 on the American Film Institute list of 100 best American films. It's on Time.com's list of 100 best films and is listed in the book 1001 Movies You Must See Before You Die. PBS has a page devoted to the film here.
There are reviews at Cinepad, FilmReference.com, Cinematical, Edward Copeland on Film, MoMA, and CineScene.
Roger Ebert says:
It is one of the miracles of cinema that in 1941 a first-time director; a cynical, hard-drinking writer; an innovative cinematographer, and a group of New York stage and radio actors were given the keys to a studio and total control, and made a masterpiece. ``Citizen Kane'' is more than a great movie; it is a gathering of all the lessons of the emerging era of sound, just as ``Birth of a Nation'' assembled everything learned at the summit of the silent era, and ``2001'' pointed the way beyond narrative. These peaks stand above all the others.
There is information on Orson Welles at Senses of Cinema, Wikipedia and ReelClassics.
Only the Cinema looks at the film.
Ferdy on Films has an article.