During our interrailtour me and my buddy Hendrik decided to stay at "Ani&Haakien" in Rotterdam - the one and only hostel we booked before starting our tour. What a good luck we did so!
First you have to say that the owners - Joyce and Daniela (hopefully I spelled it right way) - are both absolutely nice. They are always helpful and you get the impression that it's important for them that you feel welcome at their place. It doesn't seem like checking in in a hostel but as if you were staying in a living community for a few days. There's a big kitchen you are allowed to use (quite important for students without much money, who need to cook sometimes I think), a terrace outside and something like a big living room with chairs and so on, where you can relax after an exhausting day.
The price is also a good argument to spend the nights during your stay in Rotterdam at "Ani&Haakien". In comparison to other hostels you get a clean room, breakfast and great service for only 18 € (six bed room).
I think it's obvious that we both were highly amazed by this hostel and if there was the possibility we would have stayed there one more night on our way back. So... if you plan to visit Rotterdam and you need some place to rest go to "Ani&Haakien".