I found this site very useful in planning a couple of multi-city trips in Europe (flying from the US) a few years ago. (A useful tip I learned from this site:

I found this site very useful in planning a couple of multi-city trips in Europe (flying from the US) a few years ago. (A useful tip I learned from this site: in Norway, for a long trip, buy the first-class ticket; it's about $12 extra but that paid for itself in free hot cocoa.) It's also useful for getting a quick overview of the train system in a country and therefore figuring out which multi-city trips are feasible. My only complaint is that for most of Europe there's a lot of "how to get there from London", which is fine if you're coming from London or elsewhere in the UK, but I'm flying in from the USA. But this complaint is a bit American-centric. I wish you hadn't posted it, though, I'm not going to get any work done this afternoon.