As I recall [1], Mauritania is the last stronghold of old-style slavery, where people legally own other people. There are many other kinds of slavery which involve people being held captive.
That said, read the article, its very interesting.
[1] From reading http://www.amazon.com/Disposable-People-Slavery-Global-Econo... a few years ago
From what I understand human trafficking and slavery are alive and well.