You can do booking yourself via the Holland National Booking Center. It's
fast, English-speaking and reliable. I suppose they have a website (it's a
government office) but when I did it many years ago I used the fax.
The area I loved to stay is between the railway station and the Dam (on the right side looking from the station, as on the left there's the red light district and dope smokers cafes). You can find all kind of hotels, from luxury to slums), you can easily walk to most of the city or catch any public transport, from boat to tram to bike.
A suggestion for all you Amsterdam-bound: I rented for a morning an audio guide (all major languages available) with a special map which takes you to many unknown places around, telling you a lot of funny things and playing related music too. Many different itineraries are available, according to your taste, and the price is not more than a museum ticket. I got mine at Ciao Holland Travel-Stromarkt 11-Amsterdam, just a short walk from railway station.