The stain from Carrie's bloody hand to the P.E. teacher's skirt switches from a smudge in the shower room scene to a full hand-print stain in the principal's office (the stain is even higher on the skirt from where Carrie originally grabbed it).
The name of the school changes from Chamberlain (the name used in the 1976 movie, visible in the background when Carrie's classmates are in detention) to Ewen (the name in the novel, visible during the prom and after).
As Sue is leaving the gym after Chris confronts her about not having Chris's back, Sue turns around to face Chris to respond to her. When Chris walks over again afterwards, Sue has not turned around completely and turns around again.
During the prom rampage, the twins (Lizzy and Nicki) are killed in the center of the gym, but then the center is seen again when Carrie throws a flaming crescent moon at Tina; the bodies of the twins are clearly gone.
The sewing machine that Carrie uses to make her dress is an electrically powered industrial one and only requires a single depression of the control to make it move. However the shot of the foot control being operated by telekinetic powers shows it being pumped up and down as in an old fashioned manually powered machine. If she were to do this with an electrical machine it would start and stop but in the film the fabric is moving forward continuously.
When Carrie pulls the lights down and sets the banner behind her on fire, a large moon falls down and catches fire as well. As it falls, wires and rigs are visible setting off the flames and not the banner itself.
The goof items below may give away important plot points.
The position of Carrie's hair changes when she is being woken-up by her mother in the closet, when she tucks her hair behind her ear upon entering the library, while talking to her gym teacher about being asked to prom, when talking to Tommy in her front lawn, and while her mother attacks her with a knife.
When Carrie is washing the blood off of herself in the bathtub and pulls her knees to herself and begins crying, there is initially a lot of blood on her left arm. The shot changes and shows her with both arms clean.