When Madeline sees Legendre's face in her wine, she begins to set the glass down with both hands, mostly using her left. In the next shot, her right hand holds the cup and her left is on the table. Also, the position of her head changes between shots, from looking slightly up to looking directly ahead.
The number 9822 appears on the door under the staircase in one take around the 42-minute mark, it is not there in the other shots in the scene.
When Madeleine is playing the grand piano (around 39 minutes), the lid of the piano is open. You can see that none of the hammers of the piano are moving - she's obviously not hitting any of the keys.
The vulture seen fluttering at the windows is really a young bald eagle whose head has not yet turned white.
Minute 46: the vulture manages to scream, loudly and repeatedly, with its beak shut.
Even though the movie is set in Haiti you can see steam coming from the mouths as if it was cold.