I'm questioning my categorization of Edison. To me, the quote I listed is a "case closed" citation. However, in light of new evidence, I think that he would best be categorized as ambiguous. It turns out that after the New York Times article was published, he disagreed with people's assertion that he was an atheist and wrote the following in a private letter:
"You have misunderstood the whole article, because you jumped to the conclusion that it denies the existence of God. There is no such denial, what you call God I call Nature, the Supreme intelligence that rules matter. All the article states is that it is doubtful in my opinion if our intelligence or soul or whatever one may call it lives hereafter as an entity or disperses back again from whence it came, scattered amongst the cells of which we are made."
If he had just said "what you call God I call Nature," I think he would still be an atheist, but he refers to nature as the Supreme intelligence. He uses a capital "S" and it was known that he was a big supporter of Thomas Paine, who was a deist. The issue of Edison's religion is explored well on his Wikipedia page.  Anyways, it sounds like he is a deist, but I know so little about deism that that I wanted a second opinion before I move him to Ambiguous.