As Brygun said, cannibalism as a significant food source doesn't seem to have been common. The two main ritual uses seem to have been to eat (parts of) deceased relatives to retain/absorb their souls for preservation, and to ritually consume especially brave/skilled enemies to gain their power. It can also be noted that some cultures have cleaned the bones of their flesh as a kind of cleansing in preparation of performing funeral rites with the bones, but without actually eating the flesh. I don't believe I've heard of using human skin leather culturally either (it's not uncommon in fiction to have villains that make leather out of their victims' hides, and there may have been historical people who have done it, but not as part of a culture, as far as I know.
In addition to the above, there's also superstitious cannibalism, like certain parts of the current day world where people with albinism are murdered or mutilated to get body parts for ritual/magic uses (and I think this includes consumption, but I'm not sure).