The train ride from Munich was fairly standard, and it took around two hours to get to Salzburg. The youth hostel (YoHo) was really good. Not expensive, the rooms were fairly nice, we each got our own keycards to the room, and the keycards also opened pretty sizeable lockers inside the dorms. Plus the bar had two happy hours each night, with pints being €2. Definitely a recommendation for anyone backpacking in Salzburg, and I'd say it was the best place we'd stayed at so far.
In Salzburg there are 'Salzburg Cards' which are €25 for 24 hours, and slightly more for a 48 hour pass, and they basically give you free entry to pretty much all the main attractions in the city, as well as free public transport. We were a bit hesitant on whether we'd actually save money with them, but figured that if we hit the day pretty hard we almost certainly would.
Our first stop was the Residenz, which was the palace for the princes (who were also archbishops) of Salzburg. The audio tour was pretty good, and the art exhibition upstairs in the Residenz Gallery was also pretty cool.
From there we went to the Cathedral, which is directly adjacent to the Residenz, and which is pretty frickin big.
There are also crypts underground where the various archbishops/princes (I think?) have been buried.
We proceeded around the standard tourist traps by goingt to Mozart's birthplace. The whole house has been turned into a museum about the composer and his immediate family, and it's a pretty interesting visit.
Upon buying the passes in the hostel in the morning, we'd been given leaflets each which listed the various attractions and discounts that the pass offers. The girl at reception had particularly recommended the Untersberg cable car, which required a bus trip out of town, but that the bus was free on the card. It looked pretty cool to check out, so we hopped on the bus to the town of Gartenau and got our free cable car trip (usually €20) up this huge mountain.
The Untersberg is 1,972 metres high (or 6,740 feet in old money) and gives a pretty spectacular view over Salzburg and the surrounding land, and also of the Bavarian Alps in the opposite direction.
On the bus trip back into town we stopped off at the Hellbrunn Palace, which was the country getaway for the royalty in Salzburg, and which has an awesome set of trick fountains in the garden. The tour of the fountains was really good, with some really awesome water-powered mechanised puppet displays. There are also hidden water jets absolutely frickin everywhere, which the tour-guide can turn on and off at various points, and most of the tour is spent getting wet and being constantly paranoid about anything in the floor or walls that looks like it could spray water from it. The tour guide usually asked the kids to stand or sit in the places that got particularly wet, but we still got hit with our fair share of water walking round.
Back into town, and the paranoia of the fountains seemed pretty pointless because it absolutely pissed it down and we got drenched anyway, eventually finding a fairly nice place to eat called Wilden Mann which served fairly traditional Austrian food and with men dressed in Lederhosen serving us.
The next day we got out a bit earlier to go see the Hohensalzburg Fortress on the last remaining hours on our cards, taking the short funicular (the oldest one in the world) up to the top of the hill. The fortress has a pretty decent audio tour and museum, as well as a marionette museum (which I didn't bother with). I'd expect it would give some fairly decent views of the city, but it was still raining heavily at the time, and it was almost impossible to make out anything through the cloud and rain. At the viewing platform at the top of the tower the audio tour was talking about various sights which were barely discernable in the mist.
The fortress also features the Salzburg Bull (Salzburg Stier), a huge organ mounted in a room on the side of the fortress, which was used to send out messages to the city, to announce when workers (presumably in the castle?) had to start and finish work, and can also be used to play music (which it did while we were there).
Again, Salzburg was a pretty awesome city, and it's extremely scenic as well. I think it helped we had the card, not only from the point of view of saving money, but also because it probably pushed us into seeing more stuff that we might otherwise have not bothered with. It helped that the hostel was fairly awesome too. Next stop Vienna.