Other than the Buhl Centre and the Second-Hand Laden d Caritas at Sankt-Paul-Gasse 12, 3500 Krems an der Donau, there is a handy online site you can use to get second-hand stuff in Vienna, Krems and probably also other parts of Austria. It's called Willhaben.
I got a Drei sim card in Vienna at €9.90. My classmate got his in Mediamart in Buhl Centre, a mall in Krems, for less than €4. Feeling terribly cheated as usual. I thought this sort of thing only happened in Southeast Asia. I guess not.
When I arrived on 13 Aug 2015 in Vienna, it was hot. I think it was up to 32 degrees Celsius sometimes. The trouble is, Vienna wasn't built for such heat. The structure of the buildings meant that most rooms had no moving air, night or day, and that made it even hotter. Worse, almost nobody had a fan in Vienna.
The meldezettel is a document of residency you must get within three days of arriving at your location. My classmates and I filled up the application form for the meldezettel differently (below left). As a result, we received a different wording under "Wohnsitzqualitat" on the meldezettel (right). I got "Nebenwohnsitz", or secondary residence. They got "Hauptwohnsitz", or principal residence.