There is a wooden boxlike thing (not sure where to buy them) that I've seen that has slots along the sides so you can just cut down to make even slices.
If you have an electric meat slicer that adjusts to the proper width, that might work.
I bake a lot of bread and my favorite thing to slice it with is the old, famous Ginsu knife. They're not good for much else, but do a wonderful job of slicing bread.