The Daily Dish (great free e-zine from the SBD online) had an article about this recently. Dr. A advises that you should stick with cheeses that have 6g of fat or less per serving.
Part skim mozzarella (shredded and in string cheese form) should be very easy to find. I love the Kraft 2% cheese, in sliced and in shredded form, and both were easy to find both on the West Coast and here in the middle of nowhere, NY. Hopefully you can find them by you, too.
I love Cabot's cheeses, especially the red-fat cheddar.