Farmer's market - semt pazarları

One way to experience Istanbul aside the tourist places is to visit a farmer's market. Since every quarter holds it's own market, you will be able to find an open market easily. At the market, one not only can buy fresh products but also clothes, household products and other bits and pieces. If you find a crowded stand, don't be afraid, take a look maybe you will be able to make a bargain. Or just a snack?
If you can find a gözleme stand: sit down, order one and then enjoy your gözleme and the hustle and bustle around you.

Here is a list of markets in Istanbul. I took the list from Cin Cevap
Location - Weekday

Bahçelievler – Monday

Bahçeşehir – Tuesday and Saturday

Bakırköy – Saturday
Near the İncirli metro station

Beşiktaş – Saturday

Beykoz – Thursday

Beylikdüzü – Sunday

Bostancı – Thursday

Büyükada – Thursday

Erenköy – Thursday

Fatih – Wednesday

Fındıkzade – Friday

Göztepe – Monday

Kadıköy – Tuesday and Friday

Kartal – Friday

Kozyatağı – Friday
Opposite of Carrefour, near Atacan Koleji.

Mecidiyeköy – Sunday

Pendik – Saturday

Üsküsar – Friday
Near private Anadolu Medical Hospital, located in the center.

Sanayi Mahallesi – Thursday

Şirinevler -

Şişli – Friday, Saturday, Sunday

Yeşilköy – Wednesday
Near the Florya water front, close to the Atatürk Airport.

4.Levent – Tuesday

The Guardian has a top ten list of markets in Istanbul. (Not only farmer's markets): Top Ten