AMTRAK Buy One Get One Free Offer (Buy from 1/7 - 2/15 & travel 2/10 - 8/28) website here

From their site:
Need to Get Away?
When you buy a ticket, a friend or family member can ride along for free. Purchase your tickets between January 7, 2003 and February 15, 2003 for travel from January 10, 2003 to August 28, 2003. Just enter promotion code H255 when prompted by the reservations system. Certain trains are excluded from this offer. Restrictions apply.

Plus kids ride 1/2 price. And if you're traveling alone, you save 25