I like Formula One races best. I've been to quite a few races (my dad's a former rally driver and loves watching races now) in the last 10 years or so (Indy 500 a couple of times, Brickyard, a F1 Grand Prix or two, and some smaller races at Mid-Ohio) and it can be pretty fun. I don't follow the drivers as much as I did when I was a kid (loved Mario Andretti), I usually just pick one to root for before the race starts and hope for the best.
I prefer horse races, though.
Less headache and sunburn at the end of the day!