One of the delights of living in Amsterdam is the readily available fresh food, bought the old fashioned way from a market. Several offer organic food or antiques and they are busy, friendly places. Everyone speaks English of course so you can browse to your heart’s content and pick up a great picnic lunch or unusual souvenir. Obvious choices are Dutch cheese or flowers; fresh fish is also good but maybe a little difficult to send home.
 

Albert Cuypstraat Market
A vibrant locals’ market in the multi-ethnic De Pijp neighbourhood. Sells everything you could think of: vegetables, meat, fresh fish, electronics, cds, clothes, fabrics, cheeses and more. Turn up after just closing time and you'll see giant herons pecking at the scraps like something from Jurassic Park. A good reason to come and explore De Pijp; many cool cafés and bars are right next to it and serve fresh food from the market. Monday to Saturday 10 am - 5 pm. Albert Cuypstraat.

Flower Market
Tulips are one of the most recognisable symbols of the Netherlands and make an original gift or souvenir. For those of you from countries with weird import of plants restrictions there are also specially prepared bulbs guaranteed not to cause environmental catastrophe. The market partially floats over the canal and is very central but watch out for pickpockets as it's busy, narrow and touristy. Daily 9 am - 5 pm. Singel, between Koningsplein and Vijzelstraat.

Waterlooplein Market
The most famous market in town sells second hand clothes, records, handicrafts and enough sheer random junk to keep you browsing for hours in a daze. A must see if in the Nieuwmarkt/Jewish District area, it lies just down from the Rembrandt House Museum. Monday to Saturday 9 am - 5 pm. Waterlooplein.

Other Markets
There are a great many squares with irregular markets, scattered all over the city:

Amstelveld: flowers and planets; Mon 10 am - 3 pm. Prinsengracht, near Utrechtstraat.

Kunstmarkt: two quality art markets; summer Sat and Sun 10 am - 3 pm. Spui and Thorbeckeplein.

Nieuwmarkt: flowers and organic food; Sat and Sun 10 am - 5 pm. Nieuwmarkt.

Noodermarkt: organic food and birds market; Sat 9 am - 3 pm; antiques and general market Mon 9 am - 4 pm. Noodermarkt, next to the Nooderkerk.

Westermarkt: general goods market; Mon 9 am - 1 pm. Westerstraat, next to the Westerkerk.