The inspiration for Jamie Sullivan's character and some of the events in the book/movie are from Nicholas Sparks' sister, Danielle Sparks Lewis (whom the book and movie are dedicated to).
When Jamie gives Landon her mother's book she says "Don't worry, it's not a Bible". In the novel by Nicholas Sparks, Jamie does give him her mother's Bible which has her favorite passages underlined.
Much of the movie's soundtrack includes music from the band Switchfoot, who at the time were really only recognized in their native San Diego, and in Contemporary Christian music circles. Mandy Moore was a huge fan of the band, and had a great deal of influence in their participation on the film. When they were approached to do the film however, the guys really had no idea who Moore was, and weren't familiar with her music (despite her status as a pop star with several hits on the charts). Once they came on board, they contributed four existing tracks to the soundtrack, plus lead singer Jon Foreman recorded a duet with Mandy Moore, "Someday We'll Know". Moore also sings a version of the Switchfoot song "Only Hope" during the play in the film.
It was originally intended to be a PG-13 movie, which included a naked version of the picture that featured Jamie's head and a model's body. The copy that is actually shown is the only one that was edited to show her with clothes. All the copies that the characters in the cafeteria have are the naked versions.