Princess Lee Radziwill, 55, and producer Herbert Ross were married Friday night at the bride's home, and then her sister, Jacqueline Onassis, threw a dinner party for them. Dancer Rudolf Nureyev and John Taras, associate director of the American Ballet Theater, were among those attending. Radziwill's first marriage, to Michael Canfield, ended in an annullment in 1958, and the next year she became a princess by marrying Prince Stanislaus Radziwill, a Polish nobleman she divorced in 1974. Ross, whose first wife died last year, has been involved with the movies "Play It Again, Sam," "The Sunshine Boys" and "The Goodbye Girl."