You didn't say you were looking for good movies based on true events so just be warned, not all of these are gems & they lean more towards the "thriller/suspense" category: Jaws - based on real shark attacks in Jersey early 20th century. Alive - 35 athletes stranded on a mountain after a plane crash for 2 months= 20 ate weeks later. Black Hawk Down Bell Witch The Movie - Not on NF yet; follows the historical accounts of the bell witch - a sinister entity that tormented a pioneer family on Tennessee’s early frontier between 1817 and 1821. The Mothman Prophecies - Based on a reported series of creepy events that occurred in a small West Virginia town in the late 1960s. Even with Richard Gere, its not all bad. Dead Ringers - movie about twin gynecologists who do naughty things based upon the story of twins Stewart and Cyril Marcus, who were found dead together of drug overdoses in their Manhattan apartment. Shadow of the Vampire - stories about Max Shreck’s real-life vampirism have persisted for decades, and inspired this movie. The Serpent and the Rainbow - Based on a true story of the scientist who traveled to Haiti in the 1980s to investigate the factual basis of alleged zombification. From Hell - Jack the Ripper was real, as for this movie, it can be considered factual if you consider Heather Graham a real actress. The Ghost and the Darkness - lioness' on the hunt for human flesh; yummy. Wolf Creek - Australian road trip goes real bad. Requiem - similar to Exorcism of Emily Rose but much better in every way IMHO.
The Town That Dreaded Sundown - not available on NF but its worth finding it on VHS. The Legend of Boggy Creek - Bigfoot on steroids. My brothers made me watch it when I was a kid and we got our first VCR. I haven't been right since.
When you guys were talking Ed Gein you forgot to mention Psycho & Three on a Meathook. Unfortunately, the title is better than the movie.
I believe Hostel, The Entity, Picnic at Hanging Rock, An American Haunting and Deranged were all based on true stories, also, but I've got to get back to appearing to be working.
Fans of Truman Capote's In Cold Blood and its "companion" films Capote and Infamous might be interested in Norman Mailer's telling of the story of Gary Gilmore - The Executioner's Song
"Inspired by" the Stanford Prison Experiments - The Experiment
And speaking of "inspired by," I've often heard that Psycho's Norman Bates was partially inspired by ol' Ed Gein. He loomed large in the horror imagination.
The most horrifying movie you would have to buy called cabin 28 the keddie murders film. This is the true story of the bloody slaying of the sharp family, in the small town of keddie in northern california mother son, daughter and friend in cabin 28 in april 11 1981. This resort had many cabins all next to eachother. No one heard or saw a thing. The walls were covered in blood, all the furniture was torn up and smashed as was the walls and carpet. Many of the detectives refused to even enter the house. The police chief on the case had to resign. It was the most horrific crime scene ever for them. Yet, no one heard a thing that night and many in quincy know things but being a small town they will not say alot. There were 3 kids in the back room left unharmed. One of them witnessed it Justin, but he was 12 at the time and to this day will not come forward. Very shocking and will haunt you but its true and to this day has not been solved.
The Girl Next Door........... follows the unspeakable torture and abuses committed on a teenage girl in the care of her aunt...and the boys who witness and fail to report the crime.
The trial and conviction of Leopold & Loeb is told in the movies Compulsion, Rope and Swoon. Here's a link about these bad boys and their incredible defense attorney. For more on this story read For The Thrill of It, The murder that Shocked Chicago.