All kitchen scraps, including meats, etc., that most people don't put in, garden refuse, grass clippings, weeds, horse and cow poo, paper towels, occasional layer of dirt to add microbes.
What I would LIKE to do if I had the funds would be to start a compost business.
In our area, we have cotton seed hulls and rice hulls, not far from us are chicken farms, and the local lake has water weeds....seems to me those three in the right proportions would make one heck of a good compost.