I have a program called US RR Maps which covers the very basic rail lines, no sidings or yards. May I suggest downloading a road map and then with your GPS reciever you can see what towns and roads you pass.
Some of the gps maps actually show train tracks. Also, those CD rom maps that you can buy at a computer store show tracks. My Microsoft Streets and Trips maps shows the separate alignments of the eb and wb tracks on the Zephyr route on the west coast of the Sierras.