The Public Theater's "Shakespeare in the Park" season begins at Central Park's Delacorte Theatre tonight with the first performance of Hamlet. Michael Stuhlbarg, who has appeared on Broadway in plays such as The Invention of Love and The Pillowman, is starring as the troubled title character. Stuhlbarg is ably supported by a talented cast, including Lauren Ambrose (Broadway's Awake and Sing!) as Ophelia, Sam Waterston (Law & Order) as Polonius, Andre Braugher as Claudius, and Margaret Colin (seen on Broadway last season in Old Acquaintance) as Gertrude.