I’ve put together the links for the national rail company websites. The links are to the English pages where I could find a link that worked. You may get switched to local language pages (or need to go to pages in the local language) to buy tickets, etc.

Austria: http://www.oebb.at/e…
Belgium: http://www.b-rail.be…
Bulgaria: http://bdz.creato.bi…
Croatia: http://www.hznet.hr/… If you have a problem, use http://www.hznet.hr/… and click on “English” at the bottom of the page
Czech Republic: http://www.cd.cz/ Schedule information available in English at: http://jizdnirady.id…
Denmark: http://www.dsb.dk/cs…
Finland: http://www.vr.fi/eng…
France: http://www.sncf.com/… Looks like you have to do this in French to find standard pricing or to buy the ticket from SNCF. Clicking on English sends you to raileurope.com with global fares.
Germany: http://reiseauskunft…
Greece: http://www.ose.gr is the link, but I can’t get it to load
Hungary: http://www.mav-start…
Ireland: http://www.irishrail… Use http://www.nirailway… for Northern Ireland
Italy: http://www.ferrovied…
Luxembourg: http://www.cfl.lu/CF… English page not available????
Montenegro: http://www.zeljeznic… This link doesn’t work, probably because of the “yu” but it doesn’t work with “me” either.
Netherlands: http://www.ns.nl/cs/…
Norway: http://www.nsb.no/ho…
Poland: http://www.pkp.pl/ basic info in English by clicking on British flag
Portugal: http://www.cp.pt/cp/…
Romania: http://www.cfr.ro/ English schedules at: http://www.mersultre…
Serbia: http://www.serbianra…
Slovakia: http://cp.atlas.sk/v…
Slovenia: http://www.slo-zelez…
Spain: http://www.renfe.es/…
Sweden: http://www.sj.se/sj/…
Switzerland: http://www.sbb.ch/en…
United Kingdom: http://www.nationalr…

Other links:
Eurostar, the chunnel train: www.eurostar.com
High speed, premier Thalys trains from Paris to Brussels, Amsterdam, Cologne: www.thalys.com