For 3.5, I just have the PHB, MM, and DMG.
I can get a few ideas though. The village butcher has joined a cannibal cult and waylays lone travelers. What should be described about his lair? Does he leave dismembered victims alive after amputating a limb? What damage would they take from hanging skewered on some kind of wrought-iron hook? Descriptions from Diablo games might also work as a starting point.
Oh yeah, if you have an imagination, it's easy to come up with some twisted scenarios. Heck, if you love horror films, there's plenty of fodder to mine there. One of my favorite adventures of all time is a combination of John Carpenter's The Thing and Alien. :)
Who is the doppelganger? Just pass each player a note saying it's not them and the party will do the rest!
ROFLMAO!