Science Blog has some research showing that Direct military interventions can slow or stop genocide. They also found that impartial interventions seemed to have no effect. Even a single country directly challenging the perpetrator of a genocide can significantly reduce the killing.
Just something to think about, especially as thousands die in refugee camps around Darfur, and an effective response to the genocide languishes. I haven’t heard of any action from Sam Brownback in a while, and that had been a pet cause, briefly.