If you are in Vienna, duck into the Julius Meinl wine bar (end of Graben) for a lot of interesting stuff by the glass, including eiswein. I forget the name, but there is another wine shop/small bar which has an ENORMOUS amount of European wine - hundreds of bottles of bottles of wine from 1920-1980. It's north-east of St Stephens, probably 200-300m away, on a lane running north-east (street may be Essiggasse).
Whites: gruner veltliner, riesling
Reds: Blaufrankisch, zweigelt, pinot noir
Top red producers (from Hugh Johnson's book): Triebaumer, J Heinrich, P Achs, Kollwentz-Romerhof, Krutzler, Moric, Nitnaus, Prieler
Whites: Alzinger, Willi Brundlmayer, Gross, Franz Hirtzberger, Emmerich Knoll, Nigl, Nikolaihof, FX Pichler, Prager, Tement
Dessert wines: Feiler-Artinger, Kracher, Velich
Easiest to find of these producers are Willi Brundlmayer, Knoll, Nigl, FX Pichler and Kracher.
Average quality is pretty high, you will enjoy. The dessert wines are incredible as well, and a lot cheaper than the Germans.
Also, if you're looking to buy the Mozart chocolate balls (a Salzburg speciality), the ones by Furst are the original and best. Silver and blue foil. There are a lot of substandard imitations (the red and gold ones), beware (there definitely is a difference in quality). It's pretty hard to find the Furst kugels though, the red and gold ones are in all the tourist shops, supermarkets, and most chocolate shops.
http://www.original-mozartkugel.com/