Yo, NASCAR is the shit early in the season, when there's really not much else going on in the sporting world. After the weather starts warming up, I'll only watch the big races (Brickyard, Charlotte, Daytona v2.0, as well as road courses where critics can see the cars turn left and right). Unfortunately, by the time the season is winding down and the champion is being determined in the final races, football's up and running.
Mid-June has the 24 Hours of LeMans, which is the other racing highlight of the year for me. And oh yeah, don't forget WRC, which runs through most of the year.
(Kinda went off-topic, but hey, we've gotta have an auto racing post in this folder at least once a month)