Steam whistles are still being made by companies like Kahlenberg and sold be Edwards, but are they still being used anywhere apart from trains and riverboats? Any factories, mills, or fire stations still using them on steam or air? Any "Nightingale" variable pitch whistles still in use?
http://www.kahlenberg.com Check out their horn section.
I know of only two places out here that sound them regularly, the Baxter mill in Weed, CA (single long bell, air) and the VFD in Coquille, OR (Sinker-Davis, two-bell horizontal, air). They are also common on factories in Mexico.