Mary Rodgers's Freaky Friday has been adapted to film three times (1976 and 2003 theatrical films, 1995 TV movie). The two main characters are switched after they coincidentally wish for the other to be in their shoes.
This is true for the movies. In the original book, the teenage daughter wakes up in her mother's body, but doesn't know that her mother is in her (teenage) body, because she is faking it to teach her a lesson...
Vice Versa is about an undersized preteen who swaps bodies with his workaholic father using a jewelled oriental skull. The boy has fun for a while but then the plot begins when he realizes he doesn't know how to change back....
1989's Dream a Little Dream exchanges the minds of a senior citizen (Jason Robards) and a teenager (Corey Feldman), which throws a little bit of both Overnight Age-Up and Fountain of Youth into the mix.
Dream A Little Dream was a bit more complicated. The mind of Coleman (the old man) entered the body of Bobby (the teenager) and took over. Coleman's body was nowhere to be found. Bobby's mind was suppressed, but showed up to talk to Coleman in his dreams. Coleman's wife, Gena, also vanished. Her consciousness showed up inside Lainie, Bobby's would-be girlfriend, but Lainie's mind remained dominant.
At approximately the same time as Dream a Little Dream was released, three other body-swap movies with the same young/old theme hit theaters: Like Father, Like Son (1987), Eighteen Again (1988), and Vice Versa (1988). See Dueling Movies.
In The Hot Chick, the main character who is an Alpha Bitch is bodyswapped with a (male) criminal. In this case, the bodies change into the other person's body, so the main character goes to sleep and wakes up in her own bed with a man's body.
The live-action Scooby-Doo movie had a scene featuring a 4-way body swapping between Fred, Daphne, Velma, and Shaggy. The bodies rotated a few times before everyone got back to normal.
The Brazilian movie Se Eu Fosse Você ("If I Were You") has a husband and wife changing bodies. It goes back to normal after the couple has sex. It warranted a sequel, when both are about to split up, their daughter is pregnant and thus needs to get married... and to make things worse, sex doesn't fix things, only gets the "husband" pregnant.
Prelude To A Kiss has Alec Baldwin as a new husband who is somewhat disconcerted when his new wife's psyche and that of an old man are switched when he kisses her on their wedding day.
The 1940 comedy Turnabout (later adapted as a short-lived TV sitcom) has a married couple inhabiting each other's bodies due to a spell from an enchanted statue. In the film (not the TV version), the voices go with the selves, so that the husband's body speaks with the wife's voice and the wife's with the husband's — as in more-recent animated cartoons.
The Australian comedy Dating The Enemy has a fighting couple (played by GuyPearce and Claudia Karvan) switch and experience life in the opposite gender's body, bettering each other's life in the process before getting their bodies (and their love for each other) back.
1996 Disney Channel television-movie Wish Upon A Star (starring Katherine Heigl and Danielle Harris) concerns two very different sisters who unintentionally switch bodies while wishing upon a shooting star. They learn to love each other, do some math tutoring, go to the Big Dance, and get their bodies back.
Detention has a temporal version of this. Sloan Fisher wakes up in her teenage daughter Ione's body in the present day of 2011, while Ione wakes up in Sloan's body... in 1992, back when Sloan was in high school. This plays havoc on the film's Timey-Wimey Ball, and is one of the factors that almost leads to the end of the world.
The Russian film Day Watch has this with two protagonists who do it to hide one of them.