The following web pages are suggested for booking a room yourself, covering 1-star up to 5-star hotels:
The Internet Guide to Amsterdam: Hotels
www.bookings.nl (for Amsterdam)
www.a1-discount-amsterdam-hotels.com
www.simplyamsterdam.nl/accommodation.htm
www.hotelres.nl
www.hotels.nl
www.hotelnet.nl (perform Search with city = Amsterdam)
www.medialink.nl/amsterdam
Feel free to send suggestions for additions/modifications to this list of hotel booking pages to ec2002@tue.nl.