For me, it's doenetwork.org (I think that's the name). I love true crime stories and this place is chock full of them. Some of them get so in your head that you can't stop thinking about them!
My personal favorite cases:
-"Princess Doe" was a teenage girl found dead in 1982 in New Jersey. Nobody's identified her yet, it's now been 24 years. Nor has her killer been arrested (that we know of).
-"Sharon Marshall" is one of many aliases used by a girl abducted by a pedophile known as Franklin Delano Floyd. This girl went by many other aliases as did her killer. She was an incredible child and was a "who's who" among high school students in 1986. Lots of twists and turns happened between then and 1990 when she was killed in a strange hit and run. I highly recommend the book "A Beautiful Child" by Matt Birkbeck to anyone who likes crime/mystery stories. It's better than CSI, trust me.
-Tara Calico disappeared in 1988. A year later, across the country, a picture of her bound and gagged was found near a Toyota van. Two more pictures turned up later. Whatever happened to her? Nobody's found out yet. She could be alive, could be dead.
This stuff is so interesting yet does cause me to lose sleep. I also fear so much for some of my friends who are now away at school because of this (especially the ladies--there seem to be more girls abducted than guys by a big margin).