If you love a good flea market, then you must visit the biggest one in NYC, the Brooklyn Flea Market in either Dumbo or Williamsburg. It pretty much has everything imaginable, from vintage clothing to furniture. Vinyl addicts have been known to score some goodies there as well. You can take a load off the feet or grab some grub from some of the vendor carts to replenish.
From April to October the Flea operates at two different locations: Saturdays in Williamsburg at East River State Park, and Sundays in DUMBO under the archway.
There are plenty of restaurants nearby as well if you prefer a nice sit down meal and just short distance to the subway.