762mm (2ft6in/30in) is a relatively popular gauge in a few countries.
Victoria, Australia, had 5 lines in 2ft6in (plus possibly a tramway or two?). 4 of these were steam hauled, and operated by the Victorian Railways. The best known being the Puffing Billy railway.
The Alishan Forrest Railway in Taiwan also operates on 2ft6in gauge, with one of their Shay locomotives now living at the Puffing Billy railway. Another of the shays is operational for special events on that line last I heard.
The Sub Nigel gold mine in South Africa also operated 2ft6in. They operated two Hudswell Clarke 0-6-0T's (both still in the region), and an Orenstein and Koppel 0-6-0WT, which is also at the Puffing Billy Railway.
In the UK, I also know of the Leek and Manifold Valley Light Railway, which operated on 2ft6in gauge (their freight stock actually used the same design 'fox' bogies as the Victorian Railways rolling stock). The line operated a pair of Kitson 'Colonial Style' 2-6-4T locomotives, and had 'transporter' wagons to transport Standard Gauge (4ft8.5in) wagons on the line.
Regards