I will be staying in San Francisco for about a week. Coming from New Zealand I've already paid an arm and a leg for airfares so I'm quite interested in backpacker accommodation options in or around San Francisco. I'm not looking for anything flash, just clean, friendly and central or close to public transport. Something similar in standard to the YHA hostels in New Zealand.
Look on www.airbnb.com. We have used this service several times and have never been disappointed. It isn't a hostel, but you can still get rooms pretty cheap. It is because of this service that we no longer use hotels.