N4JRI's Rail Bibliography
Most of thes books are available at larger bookstores and hobby shops
Compendium of North American Railroad Radio Frequencies (Sturm) - The best frequency compilation out there. Includes some system information. From the publisher of Trains magazine.
Field Guide to Trains of North America (Gerald Foster) - Another outstanding field guide thanks to Gerald Foster's adaption of the Petersen Field Guide system of identification. Diesel locomotives look incredibly alike, and Foster's field guide is much more user-friendly than Kalmbach's Diesel Spotters Guide.
The Train-Watcher's Guide to North American Railroads (Drury) - Best basic reference on specific railroads out there. Updated every few years. From the publishers of Trains magazine.
American Shortline Railway Guide (Lewis) - Best basic reference on shortline railroads. Updated every few years. From the publishers of Trains Magazine.
The Railroad, What it Is, What it Does (Armstrong) - A text for railroad workers in training. Heady stuff, but will satisfy the most relentless curiosity. Published by Simmons-Boardman Books, Inc. 1809 Capitol Avenue. Omaha, NE 68109. (ISBN 0911382046) Not sure where to look for this, since I didn't see it on Opengroup. I bought my copy at the B&O Museum in Baltimore, MD.
Magazines:
Trains - Probably the most popular of all the train magazines. Available at most larger newstands.
Railfan & Railroad - My personal favorite. Visit their outstanding links page.