Red sand beach--hard to get there, hard to find, but not crowded, no gawkers. See my entry on the Drive to Hana.
Little Beach--very well known, crowded at Christmas-time, but fun as everyone was very laid back and it didn't seem to have many gawker-types--most peaple came in couples (except the gays). Seemed to be at least 50% heterosexual, though, which surprised us. All ages, shapes and sizes, so you didn't have to feel intimidated about "perfect" bodies. We had a fun afternoon there. Southwest side, south of Makena.