Sardinia is a wonderful island and there are many unofficial naturist spots since many years. The news are that right in these days two great beaches have been officially designated as naturist.
Porto Ferro is near Alghero 40°41'11.0"N 8°12'17.9"E, Piscinas 39°31'29.2"N 8°26'12.4"E is in the West coast.
Another one is going to be designated soon in the Southern coast.
There is only a naturist campsite for now in Sardinia, but a great increase of naturist tourism is expected. If you're looking for more information on these or other naturist places in Italy you are welcome.