BILLY JOEL’S JOYFUL REBOUND

LIFE is good for Billy Joel (above). Just a month after separating from wife No. 3, Katie Lee Joel, the Piano Man is dating Alex Donnelley, the former star of “The Young and The Restless.” Joel — who continues to break records touring stadiums with Elton John this summer — met Donnelley through friends backstage at his recent Washington, DC, concert. “The two hit it off immediately,” said an insider. The actress has been visiting Joel at his home in Sag Harbor, where they go boating or ride around on Joel’s custom motorcycles.