Put your best foot forward. Piperlime and Soles4Souls present "Give Shoes Be Merry" to help the less fortunate. Donate gently used shoes at drop boxes in Grand Central, Mars 2112 lounge and the Flatiron District (on 23rd St. and Fifth Ave.) and receive a $15 gift certificate to Piperlime. 8 a.m.-6 p.m.; free admission. Visit http://www.soles4souls.org/ for more information.