We went with Ciclismo Classico, I recommend them very highly on all counts. www.ciclismoclassico.com

I picked them because their focus is on Italy, their groups are relatively small, and they're seriously into cycling (they have daily clinics to teach you better skills, offer a choice of road bikes or hybrids, which some of the companies don't, offer lots of extra loops so you can ride a little or a lot).