Simply put, humor dealing with race. This can be a good or bad thing. I'm sure we all know what bad racial humor is. The problem currently is that no one is doing good racial humor. Some examples of this are Lenny Bruce's bits about race, SNL sketches involving Eddie Murphy, and this joke that I just love:

A black man moves in next door to a white man. One day while the black man is mowing his lawn the white man comes out to the fence and watches him. Every time he passes by the black man smiles and says, "I'm better than you." Eventually, the white man gets angry and shouts, "Why do you keep saying that? Why do you think you're better than me?" The black man replies, "Because I don't have a nigger living next to me."

Currently, at least in the US, it seems that people are afraid to offend people so the topic is ignored. IMHO, this makes the situation much worse. I agree with Lenny that words only gain power when people give them power like this.