I want to strongly recommend Haenk's Airbnb. It is well furnished, it is located in the hub of the city without being in Dam square. Even the block is quite and well connected by public transport. Beyond that, I believe Haenk is a special host: he knows every secret of the city, therefore he is able to give guests every help they need.
Further, Haenk offers bikes for free to his guests and in Amsterdam this is paramount.
In conclusion, if you wish to get to Amsterdam and you are looking for an accomodation, you have to try Haenk's.