When we were growing up our birthday cake choices were chocolate, vanilla or strawberry (or Fudgie the Whale if we were really lucky). Nowadays kids request theme birthday cakes and especially for the toddler set, trains are high on the list.
While we love the Williams-Sonoma Railway Cake Pan, if you have a small kitchen, you may not want to store a pan that will probably only get used a few times. Using loaf pans (or mini loaf pans) which you probably already have and some creativity will turn out a train cake your kid will love.
RobotJumpingRope is a great example. Like her, you could use oreos, lifesavers, pretzels, animal crackers, or insert your favorite candy here.
(Insert happy birthday kid here).
For more inspiration, search for "train cake" at Flickr and set aside about an hour.