Dear Jude,
As far as I know there aren't too many "friendly" GA airports in Italy.
About your trip I would suggest you to rech Italy from the French riviera. A fuel stop in St. Tropez (La Mole) would be nice and intresting (if you're not concerned, of course, of fuel prices which are incredibly high either in France and Italy). Once airborne from St. Tropez you'd just need to follow the coast VFR, passing over Genoa, Pisa, Rome, Naples, Reggio Calabria and then Sicily.
Even with a VFR flight plan you will be probably required by ATC to maintain 1000/2000 ft. AGL (actually flying IFR you could get a little higher clearance), especially near the Rome area in order not to disturb the Rome Fiumicino and Ciampino airport traffic.
I'd suggest you to make a fuel stop in Pisa (that's also a nice place to spend a couple of hours as the downtown is only minutes away from the airport). I would suggest you NOT to land neither in Rome Ciampino nor in Naples Capodichino as they're just busy airports with lots of police, paperwork etc. I'd rather suggest you to make fuel in Salerno Pontecagnano airport and then directly in Sicily (you'd better land in Catania rather than Palermo). From Catania you can probably make it to Malta: otherwise you could make another stop in Trapani Birgi airport.
Instead of the west coast of Italy, anyway, I'd suggest you to fly along the east coast which is actually more friendly and less congested from IFR traffic of big airports.
Arriving from France you could make a stop in Brescia-Montichiari airport. After that everything is fine: Fano is a very nice grass strip (I'm not sure about fuel availability), but you can land with no problems in Rimini, Pescara, Ancona. You could cross Italy VERY VERY south by maiing a stop in Lamezia Terme airport and then Catania, Sicily.
Before landing in each airport remember to make a phone call to each airport (just to make sure you'll have assistance with fuel, customs, parking). You can find all phone numbers in the AIP or (easyer) in the Jeppesen. You could also consider to buy a Jeppesen Bottlang trip kit for Italy.
Please let me know if you need further help.
Ciao