Some of you who use Google Sketch -Up may be familiar with Google 3D Warehouse.
All kinds of 3D models of everything from bridges, buildings and even locos.
Ralph
http://sketchup.google.com/3dwarehouse/
Here is The Golden Age of Rail.
http://sketchup.google.com/3dwarehouse/cldetails?mid=4bd692e40e73adb12ffe1766e521736b&ct=hpr1
Another nice rail collection
http://sketchup.google.com/3dwarehouse/cldetails?mid=e3581ca9e99f894e32bc0ad7b608f51d&ct=mdcc