Warsaw's shopping has diversified considerably since 1989. The centre has several large malls (Złote Tarasy next to the Palace of Culture is the most central), but the more interesting shopping is in the independent shops along Nowy Świat and Mokotowska Street, and at the weekend markets.
The Koło flea market, running every weekend in the Wola district, is one of the best flea markets in Central Europe — sprawling, unpredictable, and excellent for vintage clothing, communist-era ceramics, amber jewellery, and old Polish posters. Get there by 10am for the best selection. The Hala Mirowska covered market nearby sells fresh produce and is worth a look on its own.
Polish amber from the Baltic coast is widely sold in Warsaw and makes a good, genuinely local souvenir. Buy from dedicated jewellers rather than tourist kiosks — the quality difference is obvious.