The sisters have a 'Dualit' toaster in their kitchen. At one point the toaster makes a loud 'ping' noise and the toast shoots out. That model of Dualit doesn't do that. It has a lever that you have to use to manually lift out the toast. It doesn't ping either, it has a dial that counts down the seconds with a clockwork grind, and then just stops.
When Sally and Gillian are drinking tequila with the aunts, Sally grabs the bottle and we hear her ask "Where did this bottle come from" twice, but the first time her lips don't move. In the next shot they do.
The Aunts tell Sally they are taking the girls to the solstice, and they return the morning after Jimmy dies talking about it. There are two solstices per year: summer and winter. It is obviously summer time by the way everyone is dressed on that night and the following days. The summer solstice is in late June. When Sally is chopping down the rose bushes that grew overnight by Jimmy's grave, Detective Hallet comes and comments that it's early for roses. Actually, in New England, June is right on target for roses. Does it say where they are located? It's filmed in the Pacific Northwest, though it is also the perfect season for roses.
When Sally writes to her sister she says that she's been married for 3 years. But her daughters are clearly older than that in the consequent montage (they're running around in the yard and dancing in the living room). If they'd only been married three years then her daughters would still be toddlers.
When Sally and Gilly first go to live with their aunts, they seem to be wearing velvet dresses as they walk to the gate of their aunt's house. When they get up to the door of the house, about five seconds later, to be greeted by their aunts, they are in wool jackets and skirts.
During the exorcism, when Gilly/Jimmy is blown back from the edge of the circle, the women are holding the brooms, but in the immediate next slo-mo shot the brooms are all laid on the floor. In the next shot, the women are holding them at waist height again.
In the garden, when Officer Hallet and Sally first meet, Sally is wearing a watch on her left wrist. When Sally looks at Officer Hallet's badge we can see her reflection, and she is not wearing the watch. When the scene continues she is wearing the watch again.
When Gillian, Sally and Gary are talking about the ring that came out of the toad, the ring is first in between Gary's fingers and then appears on his index finger and alternates between shots of him and Gillian.
When Sally is on her way to her store for the first time you can see her wearing a green dress with no socks. Although Sally is still wearing the green dress when she walks in the store, after she sees her children in the window she is wearing a white dress with flowers on it and socks.
After the exorcism Sally and Gilly take the cauldron from two women. It has just been taken from the stove and they are holding it with cloths. When they go to tip it up, Gilly holds the bottom of the cauldron in order to tip it up.
The goof items below may give away important plot points.
After burying Jimmy the sisters go back towards the house with their shovels, there is a scraping noise when the shovels drag against the ground. A few seconds later, the sound is still there yet both of their shovels are off the ground.
When bringing the dead Jimmy into the house, they go the put him on the table. There are many items on the table, such as a white bowl, but in the next shot they disappear as they throw Jimmy onto the table.
When all the witches are jumping off of the roof in the end of the movie, you can see one's feet step right up to the edge of the roof, and an iron ledge. Yet when the camera shows them all from the front, they are clearly still behind a low iron barrier.
We see two almost identical shots of the left side of Jimmy's head in his revival scene, one before they begin doing the mouth sound and one just after they begin chanting. In the first scene, Jimmy clearly has a cut or scrape on his left temple, and in the second one it's gone.
In the scene when the women are in the circle, near the end of the film, Sally notices that the spell is hurting Gillian and tells the others to stop it. She does this while standing still in her place, in the next shot she has ran half way round the circle and returns to her place even though we never see her move. The background music also jumps at this point as well.
Near the end of the movie, when all of the women are standing in a circle with their brooms, the brooms go from being in the women's hands to being on the ground to back in their hands again when Gillian/Jimmy lunges for the outside of the circle.
When the coven of women are attempting to exorcise Jimmy's spirit, the equipment which causes the pictures on the wall to move (the ones which the children supposedly removed prior to this scene) is visible.
The night of the murder, there are several very prominent shots of (and verbal references to) a full moon. Only four evenings later, as the murder is being investigated, Sally looks out at a very thin first-quarter crescent moon. In reality, such a moon would not appear until more than two weeks after a full moon.
When Sally is drawing the star on Jimmy's chest you can see the outline of the star in black before she covers it with whipped cream. This is not actually a goof, as Sally tells Gillian to "get something white to write on top of the star". Obviously one of them drew the star first as a guide.
Near the end, when all the women are standing in a circle with brooms end to end, in one scene it shows the pictures on the wall bouncing around. One shot shows the wall going in and out, without the picture on it. You can see the obvious sheet rock, perfectly cut out to match the picture that's not there, going in and out.
At the end, when the ladies are all trying to vanquish Jimmy's spirit by cutting the sisters' hands, the same shot of the women being knocked back by a blast of light is shown twice, once as soon as the sisters grab hands, and again after the others form the circle.