Military fares (families too)
Another national fare to add to the list above:
10% Discount for Military Personnel
Active duty US military personnel, along with their spouses and their dependents, are eligible to receive a 10% discount off most Amtrak rail fares in the US, including for travel on the Auto Train.
Mysteriously, when I called and tried to use V626 on a ticket from NY, the agent told me it wasn't valid (she said "a lot of people have been trying to call in and use that code even if they're not travelling to Rhode Island), but then said she could still give me the greater discount of 20% off for being military.