This article in The Atlantic, "American Slavery, Reinvented" is depressing, but it is also important. I particularly like this quote from the thirteenth amendment of the US constitution:
"Neither slavery nor involuntary servitude, except as punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction."
This quote explains the private prison system in which prisoners work for multi-national corporations. It also explains the increasingly harsh sentences, and the new trend to criminalize ordinary human behavior with prison time for non-crimes like inability to make child support payments: the prison industrial complex needs more slaves.
How long will we tolerate this inhumanity?