Hostels in Amsterdam are generally good and clean, but dorms can be noisy, especially in summer months. The hostel of Hans Brinker (www.hans-brinker.com) offers cheap clean beds in the middle of Amsterdam. If you’re not interested, the sarcastic website is still worth a visit. An alternative is Flying Pig Downtown Hostel (www.flyingpig.nl), which is conveniently located near Amsterdam Central Station and also relatively cheap but the dorms are very large.
For more information about hostels see also the site of I amsterdam