A bible for rail travellers
Thomas Cook European rail timetable: A key volume for all rail travellers in Europe. Updated monthly it is the most comprehensive source of railway information for Europe.
Rail fare calculator
Rail fare calculator: this site is a superb tool for working out the standard train fare from X to Y.
The man in seat 61
Nicely eccentric and impressively detailed site with a focus on how to travel by train.
The railways of Europe
Railways of Europe: Conceived with train buffs in mind, but actually a hugely valuable resource for the ordinary traveller.
Timetables from Deutsche Bahn (German Railways)
Checking train services across Europe: Deutsche Bahn timetables