Best of Italy - 2004
Italian Glory - 2007
Italy in 17 Days - 2010
Best of South Italy - 2011
Sicily in 10 Days - 2013
Village Italy - 2014
My preference when traveling to Italy is to do the bulk of my exploring via tours. As a solo traveler, this provides a nice safety net, plus I don't have to worry about booking individual hotels, finding local guides, or transportation. That doesn't mean I don't do some of this, as I usually bookend my travel with a few days on my own. I just like using tours as a means of exploring new areas. Plus you meet some great people.
After one OK tour followed by one really bad experience , I discovered Rick Steves' tours (http://www.ricksteves.com), which are fantastic. Unlike many tours, Rick Steves' doesn't up sell add-on excursions as a way for tour guides to make additional money. His tours simply include the extras other companies often charge for on top the cost of the base tour. No surprises. Also, if you've already seen a site being visited, his guides will help you plan alternative excursions, which is a nice touch. My impression is that Rick Steves' want to make you comfortable striking out on your own.
Based on the three tours I've taken through Rick Steves' Europe Through the Back Door, Inc., I highly recommend the tours and his company.