Damo mentioned Wendell Scott, and Richard Pryor made a fantastic movie about his life story. He was the first black driver in NASCAR, and this was in the midst of the Civil Rights era, in a sport inherently tied to the South. During his racing days, he was certainly discriminated against, and treated with complete disrespect as a driver. Is NASCAR a racist sport? It certainly was at one time, but we live in a completely different era, and society's views have certainly come a long way from the 60's in the South, and across America, for that matter.
There are not currently any black drivers in NASCAR, and I don't think there are any women drivers in the Nextel Cup Series of NASCAR, maybe one. It's not a popular sport among the black community, but when I lived in Memphis, the young black males were all into wearing the racing jackets of NASCAR... I don't know what that was about, it seemed a bit odd to me, but they all had their "colors" and wore them with pride.
I've covered many NASCAR races, and I have seen some black people at the races, not many, but there were some. In fact, one of the best times I've ever had at a race, was when I camped out in the infield of Talladega, and met a black couple who were big into racing. I never saw any trouble, never saw any fights between blacks and whites, never saw any discrimination, never heard any racist remarks, just 150,000 die-hard race fans, happy to be together in one place.