European Hostels - suggestions and advice (pretty please!)

[wrldtravlr2]

I'm traveling around Europe with a friend in August and I would like any suggestions of decent hostels in Prague, Vienna, Berlin, Amsterdam, Paris, Belgium, and Barcelona. Ideally, the two of us like to stay pretty close to the central part of each city but if it's really great we'd be willing to be in non-central neighbourhoods.

Also is a price range of 25 - 35 Euro per night average/low/high for hostels during the month of August?

Thanks very much in advance!