The Wednesday Flea Market, near Ajuna beach is one of the largest temporary markets I've experienced. Packed full of the typical stuff, there are still some unique items to be found. Closer to the beach are the stalls run by the "hippies" with a variety of new and used items. Within the market are the tented Tibetan jewelers, who are reputed to have the better quality choices. Give yourself a few hours as there's lots of interesting things to see, including all of the tourists from many parts of the globe.