According to Free the Slaves, there are ~27 million slaves in the world today. That is more than at any other time in history, despite it being illegal in pretty much every country of the world. It seems that most of these slaves are used in farm work or as domestics, though some are used in mining or the sex trade as well. There are slaves in almost every country in the world, including the United States, which is estimated to have over 10000 people living in slavery at any time (from Free the Slaves).
I came across this project, which is looking for funding to create a comic book about human trafficking and needs $8000 before the end of September to make it happen. Personally, I think it looks like a good way to introduce children to the problem and raise awareness of it across the nation. It could be used as part of a unit on slavery, as a resource that is easily readable and interesting.
I'm supporting it-I hope you will too.
Borderland: A Comic Book About Human Trafficking