Avant-garde, socially conscious exhibits -- all by living artists -- fill the space here. The well-stocked bookstore and the free basement gallery devoted to interactive art (all of which can be touched) are more than enough to get you in the door. Readings, performance art, and film and video screenings often take place here. COST: $6; half price Thurs. 6 PM-8 PM. Subway: R, W to Prince St.; F, V to Broadway-Lafayette St.