@kdelint - There is a suggested internet article a few posts below, from @xyphax on learnitaliano.net. I prefer http://italian.about.com/library/fare/blfare117a.htm in which the English is clearer! But in my opinion, you can't beat a good well-presented grammar book - BBC Talk Italian Grammar is great.
Well actually...to adress people formally in Italian you use the pronoun "lei", in the third person. The pronoun "voi", plural you, to adress one person formally exists but it's not used anymore and it would be pretty weird if you used it. You only hear it in films when there are people addressing members of the nobility.
I thought 'vi' meant "you" in the plural. It could mean "I love you all" but does not necessarily. It is perfectly possible to just say "I love you" in English to a group of people, meaning several of them but not all. One of the delights of English that allows one to say something that is ambiguous?
The formal verson of "you" in Italian is "lei", the same pronoun that means "she". So to adress someone formally you use "lei" and talk to them in the third person.
"Voi" to address a single person does exist, but it was much more common in the past, now no one uses it and and it would be pretty weird. In some parts of southern Italy, like in small towns, you might find people who still say it but that's about it.
Since you mentioned aristocrats in movies, that thing in particular is the same in Italian. In Italian dubbings members of nobility are addressed as "voi" too. I don't know if this would happen in real life too though, since we don't have a nobility to adress anymore.