There is a gate in the background in one of the beginning scenes, after Sherry initially hurts herself on the clamp. A banner on the gate reads "labor will set you free", just as the gate into Auschwitz read.
Hadley Watson is the manufacturer of the Mangler, it's displayed right on the front. Each of those words have 6 letters in them. There is a big 6 right underneath those words. That's 3 6's. 666 is the sign of the Beast.
The trivia item below may give away important plot points.
Just after Adelle Frawley's accident, the crime scene photographer is seen wearing a similar hat and a scarf with the same colors as Freddy Krueger. Robert Englund (Bill Gartley) played Freddy Krueger in the Nightmare on Elm Street films.