In the last 5 years, I've been touring these countries for about 10-14 days each summer (I live in the UK, so I'm lucky to have it on my doorstep), and I think I've seen most of the popular destinations, including-
Germany: Rhine valley; Heidelberg; Berlin; Hamburg; Lubeck; Koln; plenty of Bavaria, (Munchen; Rothenburg ODT; Fussen; Garmisch; Landsberg am Lech; Kloster Andechs; Nurnburg; Berchtesgaden)
Austria: Wien; Melk & the Wachau valley; Bad Ischl; Hallstatt; Wolfgangsee; Salzburg.
Switzerland: Berner Oberland, in particular Lauterbrunnen/Grindelwald and surrounding area; Bern; Luzern; Engelberg; Zermatt;
Also nearby: Budapest; Stresa and the Borromean Islands on Lake Maggiore.
Fantastic time I've had on all these trips, but I'd be interested to hear from anyone where else they might recommend for this year. For myself, I've had a few places/things in mind that I wouldn't mind visiting, either in this or future trips, any comments appreciated:
Tirol area around Innsbruck
Black Forest of Germany
Glacier express trip - perhaps with another short stay in Zermatt, but not sure which destinations are worth visiting at the other end, or indeed anywhere in eastern Switzerland/western Austria.
The Italian speaking southern tip of Switzerland
South Tirol/Dolomites (but this seems problematic, as there doesn't seem to be any hostel style accommodation in the Castelrotto/Ortisei areas I'd like to stay in)
Just a few details - I will be travelling with Interrail, staying in hostels/backpacker hotels, I don't fly, but I don't mind zigzagging about from location to location, especially if there's a night train in between - done this plenty before!
I had got the idea of visiting Scandinavia this year, but have ruled it out as it's a lot of train travelling just to get there and back. If I was visiting northern Germany, I'd happily take in Copenhagen, but having already seen Hamburg recently, I can't think of anywhere else.