Check http://mishmashhostel.com/ to find out the best hostels in Warsaw. We have two localisations and it's really difficult to say which one's better:
Nowogrodzka Hostel - situated at the corner of Nowogrodzka and Poznańska Streets, just a stone's threw away from the Centrum Station (Warsaw Underground M1 line) and the Warsaw Central railway station, almost at the base of the Palace of Culture and Science, one of the most recognisable Warsaw's landmarks,
Old Town Hostel - around 100 m away from the Old Town Market Square, within the premises of the historical city core, right at the famous Warsaw escarpment.
This hostel is great for those of you who like to travel by trains, as its proximity from the Warsaw Central and Warsaw Śródmieście railway stations makes it not only a superb destination on its own, but also an excelent starting point for trips to other places in Poland - not only in close vicinity of the capital. The famous cities of Kraków and Gdańsk are only a couple hours away from there! It is situated on a backyard side of a modernised historical tenement. A variety of rooms in different standards are available here at a good price.
This hostel is situated near the Old Town Market Square, in one of the tenements carefully rebuilt after the World War 2. This hostel is great for those of you who like to have everything within a hand's reach - almost all the major monuments, museums, parks and nightclubs are a couple minutes away from here.