Incredible how mired we are in modern musicals!
The act one opening of My Fair Lady -- "Why Can't The English," Camelot -- "I Wonder What the King Is Doing Tonight," The Sound of Music...ummmm....
The West Side Story opening through the Jet Song if you're really ambitious.
If you're looking for overtures, there are two that stand head and shoulders over everything else: Gypsy and Candide.
I have to say I agree with the poster who mentioned the opening of Grand Hotel...
I can't believe no one (including me) has mentioned Tradition from Fiddler yet either...
Hi, Shirley Temple Pudding.