Trondheim Interrail Center
Trondheim
Norway
I failed to get any contact info from these folks, but quite frankly, you don't need it. When I asked how many beds they had, they gave me a number, but they qualified it by saying "but we've always got extra mattresses if more people show up." So, no worries, just find it and you'll be fine. If you come in via train, you'll probably be handed a little yellow flyer by one of the hostel employees, anyway, so you'll have no trouble finding it. And if all else fails, just ask for it, Trondheim isn't that big a place and most people probably know where the hostel is.
The TIRC is the university's student center during the school year, so I don't think the hostel operates during that time. When it is operating, however, it's a friendly, social place with the cheapest prices around, both on accommodation (95NOK) and food (39NOK for dinner, free breakfast for guests). The only real gripe I had with the place was the bathrooms, which were kinda gross. It's not enough that it would keep me from staying there again, however, if for no other reason than that it was a laid-back place with a great staff. Oh, and they offer free internet access, which is a big bonus in my opinion.