On Hillsborough street (right beside NC State's main campus) there are a few coffee shops that I know are decent for studying/working: Cup a Joe, Global Village, and Liquid State. There's also Jubala Coffee on Hillsborough street, though I only went there once for breakfast, and there's another Cup a Joe in Mission Valley (the shopping center between Main Campus and Centennial Campus). There are also quite a few Port City Java coffee shops, as well as a Starbucks, sprinkled throughout both campuses, which can be convenient places to get work done.