Robert Spencer writes of religion and slavery in world history, including:

[T]he pressure to end [slavery] moved from Christendom into Islam, not the other way around. There was no Muslim Clarkson, Wilberforce, or Garrison. In fact, when the British government in the nineteenth century adopted the view of Wilberforce and the other abolitionists as its own and thereupon began to put pressure on pro-slavery regimes, the Sultan of Morocco was incredulous precisely because of the audacity of the innovation that the British were proposing: “The traffic in slaves,” he noted, “is a matter on which all sects and nations have agreed from the time of the sons of Adam . . . up to this day.”

…

There is evidence that slavery still continues beneath the surface in some majority-Muslim countries as well—notably Saudi Arabia, which only abolished slavery in 1962, Yemen and Oman, both of which ended legal slavery in 1970, and Niger, which didn’t abolish slavery until 2004. In Niger, the ban is widely ignored, and as many as one million people remain in bondage. Slaves are bred, often raped, and generally treated like animals.

Some of the evidence that Islamic slavery still goes on consists of a spate of slavery cases involving Muslims in the United States.

[From FIRST THINGS: On the Square » Blog Archive » Slavery, Christianity, and Islam]
The entire article provides important historical and religious perspective on a practice that most tragically has not yet ended.