With her pooch in tow, the Gossip Girl star celebrates her 21st b-day on the New York City set of her show. Plus: Ashlee Simpson, Lindsay Lohan, Paris Hilton and more

GOLD STANDARD

Kid Rock's performance is off the chain! The singer joined Southern rockers Lynyrd Skynyrd on Good Morning America's summer concert series on Friday in New York City for a raucous run-through of the band's hit "Sweet Home Alabama."