STF Vandrarhem Nykoping is a small and friendly hostel located in Nykoping, which is famous for its proximity to Skavsta airport (which Ryanair lists as Stockholm). The hostel shares a wooded lot just a few blocks outside of downtown Nykoping with an art museum and a pond. There is a picnic area and even a parking lot on site, and it is near the riverwalk. The town center has a lot of cute shops and restaurants.
This red, wooden hostel looks like an old barn or schoolhouse. The entrances to both the hostel itself and the rooms are secure. Dorm rooms are smallish and include a fridge and dining table. The lower bunks have reading lamps. There are no lockers anywhere on the premises, but the hostel seems to attract a mature clientele, and you could probably ask to leave things in the office. There are plenty of WC's and showers in the corridors.
The comfy common area has a TV with plenty of books (in Swedish), couches, and dining tables. It seems that you can eat either in the kitchen or upstairs in the common area. The communal kitchen is extremely well-equipped with such useful things as a colander, cutting board, an extensive collection of dull cutlery, a microwave, coffee machine, hot chocolate dispenser, stove, and oven. (If you're having trouble getting power for the stove or oven, just remember to turn on the timer -- this is a very secure range!) The kitchen is pleasantly decorated, and there is plenty of room for eating your food and meeting fellow travelers.
Guests are required to clean their rooms before departure and cleaning equipment is available. If you don't want to clean, you can pay a small fee and they will clean it for you.
Since we arrived without a reservation, there was only room for us for the first night, but the friendly owners helped us to find another hostel in a nearby town that was just what we were looking for. They even called and made the reservation for us!