The Saronite Mine Slaves can be found working in the Saronite Mines in Icecrown. They are being forced to work by Foreman Thaldrin for the Scourge. They are all being afflicted by the Mind Whispers present in the mine.
10 slaves must be released for the quest [80] Slaves to Saronite / [80] Slaves to Saronite. This is easier said than done, as some will attack you, fearing you will take them away from his voice. Others will try to escape further into the mine to find him, their minds having been broken.