Phantom of the Paradise is ingenious. I love how Paul Williams takes Winslow's "Faust" and makes a bubble-gum-pop version with "Upholstery". I often break out from "Upholstery" into "Faust" because of that chorus.
Oliver! from 1968 is a great musical. "Who Will Buy?" has been stuck in my head ever since I watched it, but every number seems to fit into the film well. Not to mention the choreography is wicked good.
Another great musical is "The Music Man". Please, if you watch a film adaptation, watch the 1962 one with Robert Preston. The one with Matthew Broderick is a clear example of shoving a falling star into a film to hopefully sell a few tickets. My personal favourite is "Gary, Indiana", but every song is memorable.