Last week I was in Brussels and stayed at the Hello Hostel. I really recommend it. If you like walking then this hostel is perfect for you because it's not really close to the center. But other than that, I was satisfied with the bed, showers, breakfast..

You find so good hotel in the center near de Grand Place on the Grasmarkt

Jacques Brel is a good one, near Botanique subway station. 18 euros a night. http://www.tripadvisor.fr/Hotel_Review-g188644-d264329-Reviews-Jacques_Brel_Youth_Hostel-Brussels.html

hostelworld.com

you could have a look at the Rembrand hostel, I stayed there one night, it is not in the best street but I would say it is rather save since I walked there at night by myself and nothing happend. many students live in this street. also it is near the city centre and not expensive!If there is no bed available via the internet, just try to call them I think they always have rooms.

I was very disappointed by Brussels. It's got a few neat attractions, but on the whole it was very uninteresting. No word on hostels though, I slept at the airport.

Do not know hostel, but recommend NH Hotel in the heart of Brussels.

I haven't stayed at a hostel but I've been told Hello Hostel is a nice one...here is the address and good luck Rue de l'Armistice 1 / Wapenstilstandstraat 1 | 1081 Brussels, Bruselas, Bélgica