Without a car, the Salzkammergut is manageable but requires planning. PostBus covers most of the valley routes on a regular timetable; the Salzkammergut Card (available in summer) provides reduced fares on buses, cable cars, and lake boats and is worth buying if you plan to use public transport extensively.
Boats on the Wolfgangsee and the Hallstätter See provide scenic alternatives to the road. On the Wolfgangsee, the boat is actually the primary connection between the lakeside villages. The ferry from Hallstatt station to the village runs several times daily to connect with trains. Bikes are the most efficient way to get between the Salzkammergut's main sights once you are in the valley, and rental shops exist in Bad Ischl, Gmunden, and Bad Goisern.