BeLight Software via the iTunes App Store offers Rails for iPad
. (Click "Buy on App Store" to get this deal.) That's $2 off and tied with our March mention as the lowest price we've seen. It's an official remake of the Shortline Railroad game.
Also available is Rails for Mac for $4.99, a $5 price drop and another price low. (Move the slider in the upper right to "Mac" then click on "Buy on App Store".)