CASH CROP: They built it one piece at a time--and invited the fans. We're talking about the Johnny Cash Museum, which has its grand opening on 5/30 at 119 Third Avenue South in Nashville. The longtime dream of Cash collector Bill Miller, who began gathering Man in Black souvenirs at age 9, the Music City museum features a mountain of memorabilia, including the icon's costumes, awards, instruments, manuscripts and classic photos, not to mention an interactive display examining Cash's life, career and legacy. At the opening, the JCM will give away CDs and limited-edition posters to attendees. "I could spend a week in here and probably not see every single thing. It's something that people that come to Nashville from all over the world will want to see," reads a quote from the music legend's brother, Tommy Cash. The JCM will be open 11am-7pm every day. (5/28p)