Continuity: Early Grayce seems to be driving two different Pontiac Grand Prix in the opening scenes; the headlights differ.
Continuity: When Kessler and Carrie are having sex at the motel, Carries right bra strap is alternately on/off between shots.
Continuity: When Early is digging the hole at night and talking to Adele, you can see the top of his pants. When he climbs out of the hole, he is obviously naked.
Continuity: The amount of vodka in Carrie's glass changes inconsistently between shots while she's sitting on the couch, watching her slides, trying to convince Brian to go to California.
Factual errors: When Brian and Carrie visit the murder scene, Carrie's Nikon clearly has a motor drive, and we hear the sound of it advancing the film, but we also see her manually advancing the film.
Continuity: Towards the end of the movie, Brad and David are eating Chinese food. In one shot, you see David open his container and fold down the flaps and hold them this way. In the next shot you see him switch it with the other container on the table. When he switches it, the container he had just opened is now closed up.
Continuity: The foursome begins the journey in Atlanta (The Georgia Dome is visible during the Breakfast Cereal Conspiracy conversation). After they've traveled 480 miles, Atlanta landmarks are still visible outside the car (Equitable building, Spaghetti Junction, etc)
Errors made by characters (possibly deliberate errors by the filmmakers): When Brian and Carrie are loading their luggage into the car to begin the trip (before they pick up Adele and Early), David Duchovny (Brian) accidentally rips the fabric on the suitcase. He stops and looks back at it, then continues with the dialogue.