Here's another for 10% off on the Empire Builder using Glacier Park Inc. 's booking
http://www.glacierparkinc.com/SpecialsAA.htm
Website special only – Book your ticket(s) for Amtrak’s Empire Builder with us and receive up to 10% off the ticket price. Use promotion code: ALL ABOARD to receive your Amtrak Empire Builder ticket discount. Special offer is only valid for new reservations. Reservations must be made through our Central reservations office at (406) 892-2525 and will not be offered through our hotel front desks. Special will end without notice and will not be given if the special is requested after it has been pulled from this website.