What about the Netherlands? There's lots to see and do there, they've got a fantastic train system, and nowhere is more than 3 hours away from anywhere else. I was there for a long weekend and saw loads of places - I based myself in Delft, and the accommodation was right next to the train station and fairly cheap. I managed to see The Hague, Rotterdam, Gouda, Oudewater, Schevinengin and more in one weekend (I'd been to Amsterdam before, but that would have been do-able too). It is in my Europe blog if you wanted to see what these places have to offer - I loved it there
