According to the New York Times, Mia Farrow pressured Steven Spielberg (who's an artistic adviser for the 2008 games) to pressure China to do something about Darfur, and it's having some effect.
For all those who said China shouldn't get the games because of it's human rights violations, I would like to point out that without the games there would be little leverage to pressure China to do something. More broadly, I think this makes the point that engagement leads to more influence, while isolation leaves us with less ability to either change or predict and situations that may arise.
More broadly still, the Olympics are about world cooperation and piece, and if we exclude large and important countries like China (or the USSR in 1980, or, for that matter, Nazi Germany in 1938)we turn it into something else. The Olympics aren't supposed to create a perfect world - they are about putting aside fights to participate in sports. And without holding the Olympics in Germany in 1938, Jesse Owens wouldn't have made nearly as big an impact. It's called the Olympic GAMES - let's not turn it into some sort of western democracy and human rights club.