When we did actually use a bomb
The BBC news has a good summary of the events of August 6, 1945. I think it's always important to remember this day - and August 9th as well - as we even contemplate the fact that the country still has a vast nuclear arsenal. And a slate of candidates who will almost all agree that "the nuclear option" is not off the table.
I want to reiterate what Brian said about Barack Obama earlier. It's frustrating to hear someone speak the truth - to be open about the fact that nuclear bombs are a bad idea - and then be attacked as "naive" and "inexperienced."
From what I understand, every time a country tests a nuclear bomb the mayors of Hiroshima and Nagasaki write letters of protest. Those are people who most certainly do not come from a position of naivete.
I know that it's entirely academic to argue whether or not the US should have dropped the bombs on those two towns. It cannot be undone. We can, however, remember the reasons our government gave and think about those long and hard before we ever even think to do it again.
We can also realize the absolute destruction that those bombs leveled on those towns - and the suffering of the people who fell victim to that destruction.
Edit: I'm bumping this to the top because I want to add a link to this Salon interview with filmmaker Steven Okazaki, who has done a documentary for HBO that looks to be as haunting a discussion of Hiroshima as any ever done before.--Brian