In honor of the release of Dan Zanes and Friends' Catch That Train! (review here), I thought I'd list a few songs about trains for kids.
(Note: references to the Island of Sodor will be summarily deleted.)
(Last updated May 23, 2006)
"Catch That Train!" - off of Dan Zanes and Friends' (DZ&F) Catch That Train!, of course
"Choo Choo Ch'Boogie" - also try DZ&F's Catch That Train!
"Wabash Cannonball" - many, try DZ&F's House Party
"Guysborough Railway" - try DZ&F's Night Time
"Rock Island Line" - try DZ&F's Family Dance
A whole bunch of songs on DZ&F's Parades and Panoramas
"Freight Train" - try Elizabeth Mitchell's You Are My Flower, also (reader-recommended) on Enzo Garcia's Breakfast with Enzo
"Little Red Caboose" - many, try Elizabeth Mitchell and Lisa Loeb's Catch The Moon
"I've Been Working on the Railroad - many, try Laurie Berkner's version on Buzz Buzz
"New River Train" - try Raffi's New River Train
"Choo Choo Train" - try Ralph's World's debut Ralph's World
"The Little Engine That Could" - try the Hollow Trees' self-titled debut (sorry, Greg!)
-- Yosi also has a "Train Medley" on Under A Big Bright Yellow Umbrella that includes some (if not all) of the songs listed above.
-- Reader BethBC also notes that James Coffey has an entire CD of train-related songs called My Mama Was a Train.
I'm sure there are more, but this is a decent start -- if you post 'em in the comments, I'll add them above.