I saw Never On Sunday on late-night TV when I was in high school and then never came across it again 'til now. It's a 1960 Greek film directed by Jules Dassin. It stars Melina Mercouri as a free-spirited whore and Dassin as the American scholar who tries to guide her onto a more moral path. The theme song won the Academy Award for best song. Mercouri won the award for Best Actress at Cannes for this role. It's dated, but the music is wonderful.
DVD Talk calls it "entertaining but dated" and says, "it charms audiences immediately with its infectious music and charismatic leading lady." Time Out says, "You can see how this might have felt joyful and liberating to audiences coming out of the uptight '50s." Emmanuel Levy calls it "A kind of contemporary “Pygmalion,” ... a culture-collision comedy with all the cliches of the genre". TCM has an overview, as does MSN. Rotten Tomatoes has an 88% critics rating.