The largest foodie event in Brooklyn (perhaps the US) brings together more than 100 vendors selling an incredible array of goodness. Seize stuffed calamari or Afghan comfort food; queue for fusion inventions like ramen burgers and pizza cupcakes; or wash down Colombian arepas (cornbread sandwiches) with lavender lemonade. Locations can change, so check the website. Most vendors accept cards.
Note that the site is exposed (bring sunblock in summer, rain-proof gear in poor weather).
Most recently the Smorg has been held in Williamsburg (in East River State Park) on Saturday, and Prospect Park (near Lakeside) on Sunday. Record fairs, the Berg'n eating hall and offshoots in LA and Japan are also forays by the Smorg, which began as an offshoot of Brooklyn Flea.