at the moment I would recommend the company drei.at. drei offers an prepaid internet data card for 15 euros. it is valid for 12 month and has a limit of 1 GB data traffic.
Buying this data card, there is no need to tell any name or adress.
you will need a USB-Data Modem.
The big advantage is, that you can use this datacard also in many other countries, such as Italy, Great Britain, Ireland, Sweden, Austrailia. They call this "drei like home".
You can buy this datacard in every drei shop in austria. see at http://www.drei.at
- so this is the best way at the moment to connect to the www if you bring with your own laptop.