My best friend and I stayed at The Casa 400 in Amstel.
Here are some photos:
The accomodation was in a school building (during the holiday period when students were no longer present). It was perfectly adequate and breakfasts were served in a large dining hall. The location was very close to the Amstel subway, which was handy.
I loved being in Amsterdam. The canal boat trips were a great way to see the city. The architecture was uniquely stunning and the people were exceptionally friendly.
Website for Casa 400 http://www.hotelcasa400.nl/achtergrond-hotel.html
Casa 400 on Facebook http://www.facebook.com/HotelCasa400Amsterdam