www.wombats.at
Wombats is a very modern hostel located about 10 minutes walk from Westbahnhof station. For €14 you get a very spacious sunny dorm room with a sparkling new bathroom.
The hostel does seem to get very full over the summer months. After my first night, I went to pay for another few nights and was told that there were no rooms available at 11 am in the morning... all booked out.
I didn't make use of my free welcome drink as I fell asleep as soon as I got there, but after talking to others who had stayed at Wombats, I was assured that all the facilities are very nice: Internet, bar, bicycle hire, and all the standard fare.
I would recommend this place but I would suggest trying to book ahead.