What’s a good resource to find out about train routes in Europe?
For example, if I wanted to travel from Portugal to Montenegro, how would I find out if that were even possible and if so, how much would it cost and how long would it take and how many transfers would I have to endure?
There is not one site, but several that you need to use for this.
http://www.seat61.com has good basic info on travelling internationally by train. I find the info on the countries’ rail networks to be invaluable. The site as well as http://www.railfaneurope.net also links to the national rail sites, which are your second source of information.
http://www.bahn.de is the German rail site and has the best search engine. It is especially good for long-distance routes.
I also like the map at Rick Steves’ site:
http://www.ricksteves.com/rail/comparetickets.htm
Note: the prices there are calculated with 1.20 USD to 1 EUR. Rick Steves also has some basic country-by-country rail info.
For some European train connections you can use http://www.jizdenka.cz to figure out ticket prices.