Which are the best online classified websites? (Istanbul)

Hi I am looking for some 'on the ground' market intel re: Online classified and buy/sell websites for Turkey, that are the equivalent to the likes of Ebay, Amazon, Expedia, Autotrader etc
I am looking for the following local market leaders in:
Property
Car sales
Classified sales/ads
Travel sales
Online auctions
Any help/advice would be appreciated.