I subscribe to two: Speedway Illustrated and Circle Track. Both of them focus mostly on NASCAR, although both do cover lower American racing classes too. Neither of them cover F1, although sometimes Circle Track might have an article about IndyCar (but rarely). Circle Track is also more likely to cover other open wheel cars like Sprint cars.
The main difference between these two is that Speedway Illustrated is more entertainment oriented while Circle Track is more tech oriented. Speedway Illustrated does have some tech articles but Circle Track will go into tech a lot deeper. As a result Speedway Illustrated is an easier read but Circle Track is more likely to give you tech that could make you faster.
As a racer I prefer the tech over entertainment, but I enjoy some of both. I bought a few issues of Winston Cup Scene but never subscribed because I wanted more than soap opera stories. Same boat with National Speed Sport News. I've bought a few issues of Racer and RaceTech but they focus on racing overseas that is too different from what I do so I haven't subscribed. But what I have seen of them is pretty impressive albeit pricey.
