Amtrak is currently offering promotions for Q1 travel on Acela and in the Northeast Regional, buy 2 get 1 free, but the terms actually say buy 4 one ways and get 2 one ways free, and each must cost $49 or more.
Acela has a buy 6 get 2 free one ways deal, with each segment having a minimum cost of $90.
Amtrak is a great way to redeem Chase Ultimate Rewards points. I recently redeemed 4000 points for a 200 one way ticket just before Thanksgiving, on the last non blacked out day (Monday night). Strangely the train was far from full. It was nice getting a 5 cent redemption value, but I generally value these tickets (or the tickets to Boston or Montreal) at $80. Anymore and I would prefer the bus, so that means the redemption value is exactly 2 cents. Better than two cent valuations can be achieved by redeeming for roomettes at 15k points, the car train from DC to Orlando at 15k points, or a one way from New York to southern Florida (20 something hours!) at 5500 points, but these aren't too convenient for me.
One can get some quick Amtrak points by doing something with Google Wallet and I think joining the email list. More details on the guest rewards site. If anyone you know is about to take a trip, also, refer them to guest rewards for bonus points.