Yes, there are quite a few flea markets in Budapest. The best one is the one in Petofi Hall in the 14th district. It can be a mare to get to, but it's a lovely market with genuine craftsmen, as well. Esceri Flea Market is also quite popular. It opens at 6am on Saturday and is probably the most serious flea market. It's a ways out, in the 19th district, and if you buy anything big you'll need a car or a taxi ride back into the city.
This is a cool auction hall, http://www.nagyhazi.hu/english/index.php, which you can get smashing deals on, too!
Budapest also has tonnes of "Angol" shops; lots of second-hand clothes. There's a big one on Rakoczi between Blaha Luzja Ter and Keleti Palyaudvar; but on the days it gets a shipment, you need to be there well in advance! Hope this helps! almost 10 years ago