This web site, Tutto Città, is an excellent site if you need driving directions while you’re in Rome. The only drawback is that the site is only in Italian, but if you can understand some basic phrases, you’ll be fine. In the coming days, I’ll provide a quick and easy translation for the site.
You can also create walking tours with this site. Simply tell the program that you want walking directions (pedonale), and the site will tell you which streets to take to get to where. You could even use this for other Italian cities — Florence, Milan, Naples, etc.