i've used negative duplicating film - it used to be called SO-132.
kodak doensn't make anymore, but you can get the exact same thing for 1/4 the price kodak used to charge from photo warehouse.
it is about the same speed as azo paper.
there is a blue cast to the end product after it is "souped" in paper developer.
i've thought of making camera negatives with it, but the all day exposure kind of kept me away.
the upside is that since it goes from negative to negative ( single step ) you don't have to deal with an internegative. the downside is that it is kind of flat, there is a loss of information, and it is slower than you would expect.