Amtrak:Official site includes schedules, fares, promotions, and reservations.
Amtrak Guest Rewards: Information on Amtrak's frequent-traveler rewards program.
Amtrak Historical Society: Includes a brief Amtrak history, selected documents, a photo archive, and society news updates.
Amtrak Unlimited: Unofficial source for Amtrak information, such as policies, train amenities, and stations served by each route. Has a photo section and discussion forum.
Friends of Amtrak: Amtrak news, legislative updates, photos and links to other Amtrak-related sites. Contributors also submit reports on trips they've taken.
MileTrak: Calculates mileage between any two or more cities served by Amtrak.
Railroad.net: Amtrak Forum: Discussion forum.
This Week at Amtrak: Weekly digest of news and opinion from the United Rail Passenger Alliance.
Trains.com: All about Amtrak: Compendium of facts and figures.
Trains.com: The Scoop on Sleeper Pricing: How Amtrak sleeping accommodations are priced. 2001 article.
Wikipedia: Amtrak: Article from the online encyclopedia.
Yahoo! Groups: All Aboard: Discussion group on rail passenger service in North America, focussing chiefly on Amtrak. Free registration required.