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 the guys arrive at the University of Austin, Kyle has a cigarette behind his right ear as they get out of the minibus and as they start their walk. The cigarette has disappeared in the next shot (when Kyle trips over himself).
Continuity mistake: The diner they have breakfast at is the Gwinnett Diner (located Northeast of Atlanta), this can clearly be seen on all the coffee mugs in the kitchen. Many of the signs along the highways were either blurred or digitally altered to go along with the story.
Continuity mistake: During one of the driving scenes along a motorway, they are driving up the right hand side of the motorway. On the other side, traffic is coming towards the camera (as it should) but there is a broken down vehicle that for some reason is facing the wrong way, as if someone reversed down the motorway and broke down.
Continuity mistake: In the first scene of the movie where you see a bird view of the city you can see the filming helicopter on the bottom right corner of the screen.
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