Google Books has several free e-books of dialectical dictionaries from different parts of Italy. There are three that I've found particularly helpful within my work.
Vocabulario bresiano-italiano, Volume I
Vocabulario dei dialetti bergamaschi antichi e moderni, Volume I
Vocabulario modenese-italiano, Volume I
The second resource above helped me translate a set of Stato d'Anime [parish census] records found in the Bergamo province. In that instance, the priest(s) used the local dialect, Italian, and a mess of Latin abbreviations, on every page of the census. This may indicate that multiple priests worked on these records during the time frame of their creation. They were progressive records, with vital events and sacraments being added at the time of each event. It was probably one of the most challenging sets of translations I've ever done.
I encourage you to explore Google Books, as more and more Italian resources are becoming available, due to a collaboration between them and the Italian Ministry of Cultural Heritage. The link below describes this collaboration and details some of the resources they are seeking to digitize through this collaboration.
Google and the Italian Ministry of Cultural Heritage reach agreement to digitize works from Italian libraries