I'm surprised anyone could recommend
2000 Maniacs while calling
Wrong Turn a crappy movie, but to each his own, I guess.

Some of my favorites (I like crappy movies) include:
Just Before DawnAmerican GothicHumongousZero BoysTexas Chainsaw MassacreCabin FeverScarecrowsTourist Trap is almost backwoods horror
These movies deal with your typical "hillbillies gone wild" and the like. Some pretty decent flicks deal with "backwoods" horror without the hillbillies, including:
SquirmEvil DeadChildren of the CornFriday the 13thAswang
And so on.
Deliverance,
Rituals,
Southern Comfort and the like I don't really consider "horror," per se, but are still worth watching.
I never really cared for the
Hills Have Eyes but it still gets a lot of love. Same for
I Spit on Your Grave and crap like that.
dmeister