Continuity mistake: The college is supposed to be Ithaca University, but in the stadium scene they fail to cover up the University of Georgia "G" in the middle of the field. There are also times when they are supposedly in other states but they are obviously in Georgia the whole time..
Continuity mistake: When we first see the padded envelope, Josh has put three stamps on it, spaced out. Then when he finally retrieves it, there are 8 stamps. Admittedly his friend might have replaced them with the correct postage, unlikely though it is, but unforgivably, the address is completely different - most noticeable is the middle line. The first time it's "5893 Tyler", and the second time it's "695 University Dr." The sender's address also changes from "Columbus St." to "549 Campus Drive".
Continuity mistake: When the band is playing in the background at El's house you can clearly see that one of the band members has a cigar in their mouth, but when the camera cuts to the band playing the cigar is gone.
Continuity mistake: In the scene in the diner, the waiter fills Josh's coffee up three quarters full, but in the next clip of the two boys, Josh's coffee is full right to the brim.
Continuity mistake: Twice towards the end of the film (as we see the bus arriving at Austin, then also as it arrives back home) the bus has a front number plate (clearly visible on the front bumper during the montage driving shots), then soon afterwards it disappears.
Continuity mistake: When Josh is calling his girlfriend in the morning (after he had this bad dream about her cheating on him) you see the snake in the background. At first it's in the left corner of its cage, the next moment it's in the other corner. (00:05:00)
Continuity mistake: When they jump the bridge they land on the left side of road (right side of the screen) when they show the shot of them walking away the car is on the right side of the road (left side of the screen).
Continuity mistake: When Tom Green is playing the guitar (after the mouse has been dropped in and the snake's head is somewhat near it) the hand with which he plays the guitar switches several times as the view of his face switches. When it's a profile view, he strums on the neck of the guitar with his left hand. When it's a straight view, he plays the bottom of the guitar with his right hand.
Continuity mistake: When the guys are walking away from the car and it explodes, from one angle Sean William Scott has his hand up under his chin, but from the reverse angle it's down at his side.
Continuity mistake: In the scene where Josh is having the dream that Tiffany is watching the tape with her friends, when the camera zooms in on Tiffany as the movie is playing, look behind her head in the mirror and you will see the movie scene where Beth walks towards Josh in her underwear. It then goes to the television, where it plays the same scene again, then continues.
Continuity mistake: Not only does Josh only put three stamps on the letter and at the end and in the dream sequence it has eight, but in fact in the same scene (at the beginning where he actually puts the stamps on), the number of stamps changes from three to eight with only a few seconds in between.
Continuity mistake: When the guys are singing in the bus and the shot is on Josh, Rubin is in the background clearly facing the rear of the bus with his head buried but only a milli-second later he is facing forward and singing himself.
Continuity mistake: In the scene where the "fat" girl is sitting on the swing flirting with the geeky guy, she smiles and has perfect, straight teeth, in no need of braces. Later, in the scene where the geeky guy is introducing the fat girl to his dad at the door, the fat girl smiles and has braces on.
Continuity mistake: When Josh and Beth are making the sex tape in his room with his camera, his legs (and some other minor parts of his body) are in an entirely different position from what is seen later on the sex tape whenever someone watches it in the movie.
Continuity mistake: There is a snake in a glass cage in the dormitory room. Several times in the same scene the snake completely changes positions in the cage.
Continuity mistake: The car has no number plate holder on it when the guys first get in it, but when they're standing on the bridge just about to jump it, the car has a number plate holder.
Continuity mistake: In the scene where the car blows up after jumping the bridge they walk away from the car and are lined up just before it explodes and after it explodes E.L. turns slightly then realises that he's not supposed to yet he quickly turns back. This is before they all turn around in unison.
Continuity mistake: When we first see Josh's letter to Tiffany, notice the handwriting. When he gets it out of her mailbox at college, the handwriting is totally different.
Continuity mistake: When Barry gives the tour and mentions the psychology department, the people in the tour change places instantly. (00:02:00)
Continuity mistake: When Kyle is attacked by his dad, the revolver his dad had disappears instantly. (01:17:10)
Answer: I found what appears to be a full transcript at http://www.tvdance.com/movie-scripts/roadtrip/ although it annoyingly lacks labels on who is speaking each line.
DavidK93