Do you want to know the offer of youth hostels (Hostel)? Here are the sites I always use before booking. Take the time to read the reviews of people. We do not all have the same criteria. For some it is safety and cleanliness above all, for others, it is the party first of all!
One of the best-known organizations. They have hostels a little bit around the world. I personally used their following hostels and I was very satisfied:
In addition to HI, I use the following search engines. Very good community and lots of reviews evaluating hostels.