DRESSING UP

30 movies with prom night scenes:

1 Carrie
2 Pretty in Pink
3 Saved!
4 American Pie
5 Valley Girl
6 Whatever It Takes
7 The Girl Next Door
8 Grease
9 Jawbreaker
10 She's All That
11 Diner
12 Buffy the Vampire Slayer
13 Zapped!
14 Rad
15 Mean Girls
16 Skeletons in the Closet
17 Napoleon Dynamite
18 Never Been Kissed
19 The Truman Show
20 The Major and the Minor
21 10 Things I Hate about You
22 In Her Shoes
23 Crossroads
24 Born on the Fourth of July
25 Peggy Sue Got Married
26 Fast Times at Ridgemont High
27 Angus
28 Back to the Future
29 The Next Karate Kid
30 Romy and Michelle's High School Reunion

Thanks to TW for the idea; I'm sure there are many more - let me know if I have missed any very famous ones