I like what I see over at our namesake URL: CrimeScene.com.
Basically, they make up a fake homicide each week (set in Oxford, Miss.) and let users try to solve the crime. They post "evidence" like autopsy photos, 911 recordings, suspect lists, etc.
You have to pay a registration fee to join, but I'm thinkin' about it. Sounds like an interactive First 48, and that's something I can get behind.
Here's a Wall Street Journal article that explains the game more.