The Skepdic Article
Argues that the Lutz's were trying to evade a mortgage payment.

Amityville - Fact or Fiction
This site argues it was probably a HOAX.

Midnight Fire: The Cover up
Explains how religion and real estate companies forced people to keep the legend going for various reasons, argues that it is definitely fake. This site suggests its own conspiracy behind it.

Amityville Murders "Official" Site
A great site with info, psychological notes on Defeo, tons of photos, and an article that looks into the myths and debunks all of it. This site argues against the hauntings. Explains that it was a complete hoax. Claims the Church was never even contacted about it more than once. Also contains interviews with writers and authors. Argues people capitalized on a tragedy. Claims there was no Indian burial ground or cemetery near the house, ever.

Committee for the Scientific Investigation of Claims of the Paranormal Amityville Horror Page
This site argues against it, with support of lawyer testimony and info about the Lutz family inventing the hoax.

Ghosts of the Prarie
An overview with photos.

Amityville Horror - True or Hoax?
Site with trivia and dubious background info. Some cool photos though.