iPod junkies can get their fix 24/7 at the Apple Store’s Fifth Ave open-all-hours flagship, which is marked by a dramatic 32-foot glass entrance. There are other branches at 103 Prince St between Greene and Mercer Sts in Soho, and 401 W 14th St at Ninth Avenue in the Meatpacking District. All are equipped with Genius Bars, offering technical help for Mac users as well as repairs.