The StayOkay is a decent place to stay- the Internet doesn't work in the rooms which sucks, but besides that it's a nice spot. However if you're a young traveler, most of the people who stay there are Dutch families on vacation, so don't expect to make new friends really or anything like that. But it's clean and well-taken care of, so it's definitely a good option.
The Stone is GREAT! I've travelled a good bit and stayed in quite a few hostels and the Stone is definitely on of the best ones. It's very clean and friendly, and located an easy walk from everything in Utrecht. Also free coffee and tea! Can't beat that!
Hostel Utopia is decent- it's in a great spot and the people who work there are very nice, but besides that it's sort of a crappy place. In the 8 person dorm I saw mice running around the room (all over people's beds and stuff), and one night the room started flooding. But the 6 person dorm is much better in terms of cleanliness (no mice to my knowledge). But it's one of the cheapest hostels in Amsterdam and the location can't be beat, but you've been warned!
The Easterner is a great hostel- cheap, small, clean, full of friendly fellow travelers, and located in the best part of town (Mitte). Couldn't recommend it more highly! The Internet is spotty at best though, but it does work. But besides that you can't go wrong here!