HostelBookers – Independent hostel booking site with no booking fees. Pay 10% deposit and the balance when you arrive.
Hostelworld.com – Has more listings than HostelBookers and they charge a $2 booking fee on top of your booking.
Hostelling International hostels – HI Hostels (previously known as International Youth Hostel Federation (IYHF)) is made up of over 90 national youth hostel associations representing over 4,500 hostels worldwide. YHA hostels in Australia, New Zealand and the UK are also part of the HI group. These hostels aren’t in the hostel booking sites so you need to check this site independently.
Hostelman.com – Guide to hostels and other cheap accommodation worldwide.