Human Rights Watch:

The US government should account for all the missing detainees once held by the Central Intelligence Agency (CIA), Human Rights Watch said in a report released today.The 50-page report, "Ghost Prisoner: Two Years in Secret CIA Detention," contains a detailed description of a secret CIA prison from a Palestinian former detainee who was released from custody last year. Human Rights Watch has also sent a public letter to US President George W. Bush requesting information about the fate and whereabouts of the missing detainees.

[..]Human Rights Watch's letter to Bush contained two lists of missing detainees. The first list names 16 people whom Human Rights Watch believes were held in CIA prisons and whose current whereabouts are unknown. The second list names 22 people who may have been held in CIA prisons and whose current whereabouts are unknown.

Human Rights Watch expressed concern about what may have happened to the missing prisoners. One possibility is that the US may have transferred some of them to foreign prisons where they remain under the CIA's effective control.

[..] Another worrying possibility is that prisoners were transferred from CIA custody to places where they may face torture. A serious concern is that some of the missing prisoners might have been returned to their countries of origin, which include Algeria, Egypt, Libya and Syria, where the torture of terrorism suspects is common.

LA Times has more. This story has come out in little drips since the beginning. I suspect that when or if the full story is ever known, the truth will be more horrifying than we can imagine. I was discussing this with a friend from Peru yesterday. The thing that we must remember is that the information is tightly controlled here, but in other parts of the world, they hear of the practices and as he reminded me, it's hard to disinguish exactly who the bad guy is in Bush's war.