Lets see what has been missed so far,
Silver Dollar City at Branson MO
the railway at Sullivan Mine in Kimberly BC
The Fort George Park railway at Prince George, BC

Some defunct/static park and narrow gauge railways come to mind:
Stuhr Museum of the Prairie Pioneer
Death Valley Baby Gauge tramway
Nevada County Traction (next door to the NCNG museum)
West Side Lumber
Laws Museum in Bishop
Alton and Pacific

Operating narrow gauge-ish or really big park train operations I might add include these:
The Baker Family's 18" gauge railroad in Alturas, occasionally open:
Argo in Alturas
(I understand this engine is in Alturas)
Charlie Lix's Lokey
Swanton Pacific
Cal Poly's Swanton Pacific
Buckhorn Northern in Loveland, CO
Buckhorn Northern
the private Descanso Alpine and Pacific in Socal
DA&P and a short tramway
At my last count there are 15-20 Homestake/Porter air motors in the West, and a few of them are operable such as this one at the Colorado Museum of Mining and Industry in Colorado Springs:
Homestake Air Motor
The Julian Train and Gold Mine operation, also in Socal
Pioneer family in a time warp
Lakeside Amusement Park
22" gauge Cagneys on a long haul

Some of the entries in the last section above are narrow gauge, others are just fun but chunky small railroads, but sometimes it is hard to tell the difference. We talk about them on the 18inch group
O. Anderson
moderator
groups.yahoo.com/group/18inch