Don;I had no idea there were so many. I remember some of
the great pop songs, Chattanooga Choo Choo perhaps best
known, but there's also On the Atchison, Topeka and Santa Fe,
Wabash Cannon Ball, City of Miami, Ballad of Casey Jones,
Orange Blossom Special, and of course, I've been working
on the Railroad.
Those are just the tip of the iceberg. Check out this
railroad song list on Wikipedia.
That'll sure keep your layout humming.