There's Formula One: The pinnacle of motorsport, with mass amounts of technology and engineering behind the cars. The championship travels all over the world sparking week-long festivities wherever they go. Amazing tracks, amazing speed, amazing drivers.
Grand-Am: multi-class road racing series known as the Rolex Grand-Am series with prototypes and GT classes. going to the race this weekend here in NJ
V8 SuperCars: Probably the most entertaining form of racing i've ever watched. So many things go wrong i find it hilarious and exciting. Almost like NASCAR, but the cars are designed for road courses. They are proof that Austrailians are fucking crazy.
Le Mans series: there's that and the American Le Mans Series, long endurance multi-class racing with 2 classes of very very very high-end prototypes and multiplie GT classes. Very cool if you're somewhat into the engineering of the cars like me
World Rally Championship: World-class Rally racing, you should know what that is. cars start one at time going through the woods over sand,dirt,gravel,tarmac trying to be the fastest on the stages. 2 people, 1 car. Co-Driver shouts pace notes while the driver turns those numbers and commands into little motions of the brakes, steering wheel, and gas pedal. Hard to follow in the US since only 1 channel covers it, " HD Theater", just google it to find the schedule.
MotoGP: World-Class motorcycle racing. Not regular motorcycles, best way i could describe it is "prototype sportbikes". incredibly physically demanding sport, most of the riders are between 15-25 years old. it maybe only 2 wheels, but there is some pretty exciting moments in it.
oh and, Rallies are fun to go to, ive been to one here in America, you're so close to the cars it's really exciting to have mud and sticks shot at you by Dave Mirra
hope this helps, there's plenty of entertaining forms of racing out there !