Essentially, just about every aspect of a car's shape owes something to motorsport. Here's a quick version:
The Kammback design was developed by Nazis, but first used by 1960s race cars like the Shelby Daytona. In essence, the chopped rear end drastically reduced the car's drag, making it more efficient and resulting in a faster top end. It's that same principle that influences the shape of cars like the Prius and the Honda CR-Z.
Ever hear of ground effects? Controlling the air under the car to help keep it stuck to the road was pioneered by Chaparral, a small west Texas race team that ultimately developed a car that in terms of sheer pace was miles ahead of Ferrari and Porsche.
Wings? Those, you probably knew, but the first started to sprout up in the mid 1960s at Indianapolis, and shortly thereafter in Formula One and CanAm.
CORRECTION: One of our readers correctly pointed out that the first known wing on a car actually appeared at a dirt track in 1959.
6. Active Suspension
The notion of the car's computers taking an active role in adjusting the suspension (i.e., in "sport mode") really took off in the late '80s and early '90s with a series of successful experiments in Formula One, culminating in Nigel Mansell winning his only world championship in truly dominant fashion over mere drivers like Ayrton Senna. Today, a car continuously adjusting itself is fairly commonplace.