A couple of things you should do if you have a little more time in Salzburg; Go to the Museum der Moderne on the Monchsberg. Go to the AugustinerBrau for really good Austrian food, good beer and cheap prices in a great environment. Go to the Steinterrassencafe in  the Hotel Stein, just next to the main bridge- you get a great view over the centre. Sit in Mirabell Gardens for a bit, you'll see all the locals sunning themselves. Have Sacher Torte, the Hotel Sacher cafe has the best but it's quite expensive. Mozart Kugeln obviously- but buy the ones from the Konditorei Furst (the silver ones) because they're the originals. Mozart's Geburthaus is quite boring, his Wohnhaus is quite cool. In summer, go to the Eisgrotte on Getreidegasse for amazing ice cream. Cafe Tomaselli isn't really that expensive; if you go have the apfelstrudel. It's immense. If you have half a day to spare go up to the Untersberg (a mountain), on a sunny day the view is amazing. Failing that the view from the Hohensalzburg Fortress good. Get a Salzburg Card- you can get in pretty much any touristy place free plus you don't have to pay for buses.