It’s all about trains!

I tend to like train trips a lot and have gathered a bunch of information and tips that I thought might be of fair use for others, too. 
Tips & Tricks
- 
    A great website that gathers a huge amount of information on train travel in Europe and the world, sorted by countries and cities: seat61.com 
 It also provides alternative roads and touristic information.
- 
    A wonderful book about travelling across Europe by train, with a suggestion of trips and alternative railways + its complementary website: Europe by rail -> Slow travel. 
- 
    Websites from which to order cheap train tickets: 
 trainline.eu
 raileurope.co.uk (formerly loco2)
- 
    To help you find alternative transportation in case train tickets are too expensive or non-existent: rome2rio.com 
Railway pass to travel in Europe
- Across Europe 
 for European citizens: interrail.eu
 for non-European citizens: eurail.com
- Spain: RENFE Spain pass 
- Switzerland: swiss travel pass 
- Balkan Flexi pass: Bulgaria, Greece, Macedonia, Montenegro, Romania -only the Regio Calatori operator, Serbia, Turkey and Bosnia Herzegovina 
- Norway in a nutshell: norwaynutshell.com
Night trains in Europe
- The different options: interrail night trains 
- Map of the night train network (last update: January 2019) 
- Austrian night trains (the OBB is pushing for the maintenance and development of night train lines): nightjet.com 
- Thello train (Paris to Venezia via Milano): thello.com 
- French night trains (in French): lefigaro.fr
- Back on track: A European initiative/network to support cross-border night trains
- The German train company has recently announced the opening of new nightlines in 2021!!

Additional ressources
- Railway gazette 
- Open railway map (all the railways in the world)
- Random: To check the access to plug sockets on Spanish trains: RENFE prestaciones
National railway companies in Europe
Be aware that in some countries, trains are not the best transportation system available and you might also want to check (local) bus companies + check visa requirements
Albania: HSH 
Austria (OBB, small prices): Sparschiene 
Belgium: SNCB 
Bosnia and Herzegovina: ZFBH or ŽRS 
Bulgaria: BDZ 
Catalonia: rodalies 
Croatia: hzpp.hr  
Czech republic: cd.cz 
Denmark: DSB 
Estonia: evr.ee (state-owned) and elron.ee (around Tallin, private company) 
Finland: veturi (VR) 
France: SNCF 
Germany (Deutsche Bahn, small prices): Preisfinder 
Greece: OSE 
Hungary: MÁV-csoport 
Ireland (Eire): irishrail 
Italy: trenitalia 
Kosovo: trainkos 
Latvia: dz.lv  
Lithuania: litrail 
Macedonia: MZT 
Moldavia: CFM 
Montenegro: ZCG 
Netherlands, the: ns.nl 
Norway: VY 
Poland: polrail 
Portugal: cp.pt  
Romania: Căile Ferate Române 
Serbia: ŽS 
Slovakia: slovakrail 
Slovenia: slo-zeleznice 
Spain: RENFE  
Sweden: sj.se  
Switzerland: SBB/CFF 
Ukraine: UR