Italy's La Repubblica has a report on the phenomenon of widespread slavery in Mauritania.
Members of an anti-slavery NGO group were jailed for protesting the enslavement of two girls, aged 9 and 13.
"White Moors," who are ethnic Arabs, are enslaving nearly 600,000 "Black Moors" in Mauritania. Last month a UN special envoy noted that slavery is still a major problem in the Islamic country. Blacks who are former slaves and others are living in real apartheid conditions, forced to live in black-only camps with poor services and suffering continued abuse from the Arab-Berber minority rulers.
Don't bother to try to find a single report on this phenomenon at the Human Rights Watch website. They don't even have a country listing for Mauritania, and their last full report on abuses in the country was written in 1994. The UN and the BBC can somehow find out about these practices, but Human Rights Watch is far more preoccupied with a certain country with a Jewish majority. (Amnesty, on the other hand, does a nice job on covering these crimes.)
UPDATE: NGO Monitor wrote about this issue a year ago.