A website called In Italy used to have all the names of the towns in alphabetical order. They removed it from their website but below are the web.archive.org links. I find the lists very useful when I can make out several letters but not the entire name of the town.
Italian Towns Beginning with A
Italian Towns Beginning with B
Italian Towns Beginning with C
Italian Towns Beginning with D
Italian Towns Beginning with E
Italian Towns Beginning with F
Italian Towns Beginning with G
Italian Towns Beginning with H
Italian Towns Beginning with I
Italian Towns Beginning with J
Italian Towns Beginning with L
Italian Towns Beginning with M
Italian Towns Beginning with N
Italian Towns Beginning with O
Italian Towns Beginning with P
Italian Towns Beginning with Q
Italian Towns Beginning with R
Italian Towns Beginning with S
Italian Towns Beginning with T
Italian Towns Beginning with U
Italian Towns Beginning with V
Italian Towns Beginning with Z