The Arizona Railway Museum has an impressive roster of equipment, and the all-volunteer organization is constantly working on restoration projects at the yard. You can see the list of locomotives, motor cars and other self equipment here.
Not all the equipment is available for viewing or for entrance during the entire year. On National Train Day (see page 6 of this photo tour for more information), you'll be able to see more, and enter more rail cars, than on any other day of the year.
The photo above was taken on National Train Day 2009. Trains pictured here may or may not be accessible during regular season visits to the museum.