Ones still performing, or including those retired or dead? Julie Andrews would still be singing except for a throat mishap, but continues to act. And in Hollywood's Golden Age, many actors not only sang & acted, but danced, too, what they called a "triple threat." There were too many to list, men & women, but among the more notable "multi-talents" would be Ginger Rogers & Judy Garland, and for the men, Bing Crosby & Gene Kelly (along with tough-guy film gangster Jimmy Cagney, who was such a great singer & dancer that he won an Academy Award for it, which always amazes me).
Not as much call for film singing these days, or dancing, and those that do it tend to come from the Broadway stage or musical entertainment fields, like Bernadette Peters, Bette Midler, or Barbra Streisand. Whereas Cher isn't known for singing roles in films, just her acting, Madonna's acting has been panned (if not banned), and Academy Award-winner Liza Minnelli only appears on stage now.