I've only ever been to Germany once on vacation, though I have passed through Berlin a couple of times on my travels. Of all the countries I've seen, it's right up top there with places I'd like to go back to though.
It was back in 2006, on my way to visit a girlfriend in Poland, that I spent two fun weeks exploring the North of Germany (Lubeck, Hamburg & Berlin). Three very contrasting locations, each most definitely worth spending more time in than I had available (and maybe with more money too, next time!).
Lubeck is quaint, with a lovely old town, Hamburg is pure industry, with HUGE canals, and Berlin is massive and metropolitan, with oh so much history thrown in! You can read more about my experiences in each city below.
If I was to return to Germany (and hopefully I will, soon), I think I'd like to see the South though. It really does look beautiful, full of forests, castles and mountains. Oh, and I'll be taking a Porsche up the Autobahn. Because, why not?!