Came across this recently:
New York Magazine ranked it 32nd among the 50 greatest dance scenes of all time. For this thread's purposes, it gets good at 3:23, when Ann-Margret grabs the blond guy's hand. We get an entrancing view of his, er, abilities. I tried to track down the name of the guy, but couldn't ID him from what I could find on line and many of the teenagers in the film weren't even credited.