A slideshow of fifteen of the photos is here. Though portions are blocked out, they are extremely graphic.
Among the shots: A picture of a soldier and four nearly naked detainees, one of whom has the words "I'M A RAPEIST" written on his buttocks; a picture of a prisoner cowering while surrounded by dogs and soldiers with guns; a picture of a naked man with an unidentified white liquid coming out of his mouth; a shot of a naked detainee with eight large red welts slightly above his buttocks; a photo of a smiling soldier kneeling next to a detainee strapped down near the floor; a photo of a naked prisoner hanging upside down from the top of a bunk bed; a picture of a soldier who appears poised to punch a shackled detainee; and pictures of what appear to be the corpses of prisoners.
Another gallery is here; it includes more graphic images.
According to the Sidney Morning Herald, the photos are among those the president said this week he does not want released out of concern that doing so could put U.S. soldiers at risk, though that cannot be confirmed.
In discussing his decision, the president claimed the photos in question "are not particularly sensational, especially when compared to the painful images that we remember from Abu Ghraib."
According to the Telegraph, photos not yet released reportedly show "military guards threatening to sexually assault a detainee with a broomstick and hooded prisoners on transport planes with Playboy magazines opened to pictures of nude women on their laps." The American Civil Liberties Union has sued for the release of up to 2,000 photos.
*UPDATE: Pentagon spokesman Lt. Col. Patrick Ryder tells USA Today that these images appeared in Wired magazine in February of last year. Here is that story, which includes some, but not all, of the shots above. In addition, the Web site Raw Story ran the photos in 2006, though it acknowledges they went "largely unseen." They were also published in Salon.