Anyone who is serious about travelling or getting to know Italy should be acquainted with the venerable Touring Club Italiano, referred to by the Italians as "il Touring." The association, dedicated to responsible and serious travel (not only in Italy) was founded in 1894 and produces what I believe to be the best guides and maps to Italy. They also offer discounts to members, on-the-road assistance, and their own tours.
Unfortunately, the whole range of their ample output of guides is not available in English. They have recently produced an update of their website (they have been online for years) with an English version. There are various membership levels. On the English-language site, a flat 25 euro International membership is offered, but there is little transparency about exactly what is entailed by this one-year offer (valid from now to the end of 2008). As I myself want to join (as I did when I lived in Italy), I will query them and get back to you.
