Made this very simple program to change an OpenPeripheral ticket printer into a touch screen ticket dispenser.
Railcraft and OpenPeripheral required.

http://pastebin.com/ezVPsbUY

To set this up you simply place the ticket printer next to the computer and place a vanilla dispenser above the ticket printer. Make sure there is a solid block above the computer so the redstone signal will be transmitted to the dispenser. Then connect an advanced monitor to the computer. A 3 tall, 2 wide monitor works well. When you potential rider clicks one of the destinations, a ticket will be printed, moved to the dispenser then ejected (you will want to position things so that the ticket is ejected very near where the rider would most likely be standing when they click the monitor). The rider can then place that ticket in the steam locomotive. The destination names should match your routing names used in the switches on your rail system.

Feel free to modify this program to suit your needs.