Good thread. I've bookmarked it.
In our RV travels, industrial sightseeing/factory tours are right next to museums in our activities. We've been to a score of wineries, several distilleries, a couple breweries, Harley-Davidson plant, Piper Aircraft plant, Ford pickup plant, Corvette plant, Toyota Camry plant, Tillamook cheese plant, an oak whiskey-barrel plant in Lebanon, MO, the USGS map-production center in Rolla, MO (where everybody stopped whatever they were doing to show and explain it to us- well hey, it's the government, they're not under a lot of pressure,) the gigantic foundry in York, PA where they were making replacement turbines for the Aswan High Dam (used to be Allis-Chalmers, now German and I've forgotten the name.) That one probably doesn't count, since my wife's cousin was the executive assistant to the CEO, and I don't think it's available to the public. They were bending five-inch thick strips of steel into corkscrew-shaped pieces to be welded together to form cornucopia-shaped volutes for the turbines. Mostly guided by hand (with powerful material-holders) under huge drop forges. Dam*dest thing I've ever seen.
We've been to the Jelly Belly factory near Sacramento, which maybe doesn't count either since it was designed from the ground up as a tourist destination. Good tour, though.
Local Chambers of Commerce can sometimes be helpful in pointing these things out. They're not as available as they used to be due to worries about liability.
I always go for 'em when I can find them. And, the wineries and breweries usually give you samples.
Mike
Factory tours USA 
I enjoy seeing how things are made and, if given half a chance, talking with the people making them. 
