In the Summer nearly all big national railway operators have special offers to discover the country. I think it might be a good idea to collect them collectively so we can plan some nice trips this summer. Here are those I am aware of:

France

Region Grand Est

• Pass Jeune TER Fluo
  Conditions: <26 Years
  Availability: July& August
  Price: 29€/Month Validity: Regional Trains (TER) only

Belgium

• Youth Holidays
  Conditions: <26 Years old
  Availability: July/August
  Price: 19€/Week and 31€/Month Validity: On all SNCB Trains

Germany

• Deutschlandticket
  Conditions: Subscription, but you can cancel every month
  Price: 49€/Month
  Availability: Permanent Offer
  Validity: Regional Trains Only

Denmark

• Rejsepass
  Conditions: Limited Contingent of 75.000 Passes
  Availability: 24. June- 21. July and 31. July- 20.August
  Price: 399DKK/8 consecutive days (~53,85€)
  Validity: Pretty much all trains and public transport on the associated companies

Sweden

• SJ Tågluffarkort

Switzerland

• Schnupper-GA
  Conditions: You need to be a resident of one of Switzerlands neighboring countries or a Swiss resident. Only one month and one pass per Person (you can get a rebate on a yearly pass if you like) Price: <25 Years: 245/325CHF for 2nd/1st Class
  >25 Years: 340/450CHF for 2nd/1st Class
  Availability: Now-31. July Validity: All trains/busses/trams etc in Switzerland, a lot of boats, and even some mountain trains, or a rebate for them\

This will be extended when I have the time. If you have additions please write a comment and tag me :)