The Disneyworld one is still there. Funny that I rode it as a kid, then I was able to take my own children on it just a few years ago.
Disneyworld also has a railroad (and the monorail) that serves a purpose of serving the whole park. I went at peak season and the railroad seemed to keep up with demand, although I think that's because it serves the "outside" of the park, and if you're wandering the inner parts of the park it's just easier to walk to where you need to go.
Of course, it was just a "ride" and only covered Tomorrowland. I've always thought they made a mistake not covering the whole park with one of these.