Here is a list I've compiled of movies where people sing in cars. Please feel free to add to it. The only requirement is that characters must be driving in the car while the singing is taking place. The question marks represent unknown song titles/artists.

Movie Actor(s) Artist Song

Say Anything - John Mahoney - Steely Dan - Rikki Don’t Lose That Number
Men In Black - Tommy Lee Jones - Elvis Presley - The Promised Land
How to Make an American Quilt - Several - Neil Diamond - Sweet Caroline
Pulp Fiction - Bruce Willis - The Statler Brothers - Flowers On The Wall
Wayne’s World - Mike Myers/Dana Carvey - Queen - Bohemian Rhapsody
Jerry Maguire - Tom Cruise - Tom Petty - Free Fallin’
Almost Famous - Several - Elton John - Tiny Dancer
Thelma and Louise - Geena Davis/Susan Sarandon - ? - ?
Chitty Chitty, Bang Bang - D. VanDyke/Sally Howes - ? - Chitty Chitty Bang Bang
Haunted Honeymoon - Gene Wilder/Gilda Radner - ? - ?
Grease - Olivia N. John/J. Travolta - ? - We Go Together
Tommy Boy - Chris Farley/David Spade - The Carpenters - Super Star
Twilight Zone Movie - ? - CCR -Midnight Special
Rain Man - Tom Cruise - ? - ?
O Brother, Where Are Thou? - Several - ? - ?
Stepmom - Julia Roberts/Kids - Marvin Gaye/Tammi Terrell - Ain’t No Mountain
Crossroads - Britney Spears/Others - N’sync - Bye, Bye, Bye
Bad Boys - Wil Smith/Martin Lawrence - Inner Circle - Bad Boys
Planes, Trains & Automobiles - John Candy/Steve Martin - ? - Blue Moon Over Kentucky/The Flintstones Theme
Rush Hour 2 - Jackie Chan/Chris Tucker - Beach Boys/War - California Girls/Edwin Starr
American Beauty - Kevin Spacey - American Woman - The Guess Who
The Money Pit - Joe Mantenga - Al Martino - I’ve Got To Be Me
At Long Last, Love - Several - Cole Porter - Friendship
The Coneheads - Dan Ackroyd/Jane Curtain - Soft Cell - Tainted Love
A Night at the Roxbury - Will Farrell/Chris Kattan - ? - Baby Don’t Hurt Me No More
Lilies of the Field - Sydney Poitier - ? - Amen
Tie Me Up, Tie Me Down - Antonio Banderas - ? - ?
A Christmas Story - Several - Traditional - Jingle Bells
Sleepless in Seattle - Tom Hanks/Meg Ryan - Traditional - Jingle Bells
Meet the Parents - Robert DeNiro - Peter, Paul & Mary - Puff the Magic Dragon
American History X - Ethan Suplee - ? - The White Man Marches On
The Sweetest Thing - Christina Applegate/C. Diaz - Rupert Jones - Escape (The Pina Colada Song)
Harold & Kumar go to White Castle - Harold & Kumar - Wilson Phillips - Hold On

Hi,
In "A night at Roxbury" the main song is "What Is Love" by "Haddaway" ("Baby Don’t Hurt Me No More" is a part of the lyrics of that song).
In "O Brother", main music is "I am a man of constant sorrow" by "The soggy bottom boys", but I am not sure that they sing it in the car in addition of the few scenes where they sing it.

I just finished watching "Oh Brother" they didnt sing anything in the cars or trucks. Fantastic movie, its got an interesting mix of old world values and new world expressions

Thanks for the updates. Some of them were told to me and I wasn't able to check them out but if you happen to come across ANY more, please add them!

In the beginning of "Urban Legend", a girl (Natasha Gregson Wagner, I think) is listening and singing "Total Eclipse of the Heart" (Bonnie Tyler) while driving a Ford: http://www.imcdb.org/vehicle_6985-Ford-Expedition.html

-In "Scary Movie", Marlon Wayans, i think, sings "It's raining men" inside the 540i
-In "Charlie's Angels: Full Throttle", Drew Barrymore and her old boyfriend (Luke Wilson?) sing together Bon Jovi's "Living on a prayer"
-In "Manolito Gafotas", David Sánchez del Rey and Roberto Álvarez sing together Azúcar Moreno's "De lo que te has perdido"

Dumb and Dumber-Jim Carrey/Jeff Daniels/hitchhikers-?-Mockingbird

Oh, and there's quite a bit of car singing in Vacation. I know one song is "Deep River" when they are going over the bridge to St. Louis.

These just keep coming to me!

Planes, Trains & Automobiles-John Candy-Ray Charles-Doin' the Mess Around

Planes, Trains & Automobiles-Steve Martin-?-Three Coins in a Fountain

Planes, Trains & Automobiles-John Candy-?-Flintstones Theme

The Flintstones-John Goodman/Rick Moranis-?-?

Corky Romano-Chris Kattan-?-?

Christmas Vacation-Chevy Chase and family-traditional-Deck the Halls

The Great Outdoors-John Candy and family-?-Yakety Yak

The Simpsons-Homer Simpson-?-Flintstones Theme

Chappelle's Show-Mos Def-Mos Def-Close Edge

I think david hasselhoff has sung to a couple of songs while driving KITT in Knightrider.!

The Lost Boys-Dianne Wiest-The Rascals-Groovin'

Also,
Maximum Overdrive> The Bible salesman is singing some song (it was: One step at a time sweet Jesus, thats all I'm asking you.....).

Thats all I can think of right now,

-Explorer4x4, Conor

Here are a couple more . . .

Updating the "American Beauty" entry

American Beauty - Annette Benning - Don't Rain on My Parade - Bobby Darin

Defending Your Life - Albert Brooks - Barbara Streisand - ?
Reality Bites - Jeanne Garafalo/Winona Ryder - ? - Tempted by the Fruit of Another
Godzilla - Matthew Broderick - Fred Astaire - Singin' in the Rain

Also, I just watched "Meet the Parents" and that entry should be removed as Stiller and Deniro are driving in the car but all Deniro says is "Puff" one time and then launches into a conversation, so it's not really singing.

Erik

In the Almodovar film "Atame" (Attache-moi) ... at the end, Antonio Banderas, Victoria Abril and Loles Leon are into a Seat Ibiza and sing a famous song but I cannot tell what title it is

In "Bananes Mécaniques" , the girls sings a "Chanson paillarde" in the Citroen 11:

Oui, je sens bien Adrien
Ce n'est plus ton p'tit doigt qui m'chatouille
J'sens ton nombril contre le mien
Et la chaleur de tes couilles

In "Click" a guy pulls up next to Adam Sandler in a Covette, over-enthusiastically singing "Working for the Weekend"

"Canadian Bacon": a failed try of "Born in the USA" sung by John Candy and the two other guys.

OK, so I watched The Big Lebowski today Apprarently Tara Reid as Bunny Lebowski sings a song that I have now forgotten. Anyone help out with this one?