Hostelworld is a nice web site for booking hostels/cheap hotels. After you specified dates, country and city, you get a list of available hostels which you can show in a map (“Open Map” in the upper right corner). You can also give/read reviews, and book online. Filtering could be better (e.g. by price), and sometimes the number of days got reset for no obvious reason. But the map-feature is a killer, and the website knows a large number of hostels.