This thread has inspired me to go looking around for tours in my area (around Dallas, TX.) and I came across this link on Google. Apparently, it can hook you up with something in any of the U.S. Hope that helps some!
Now, or at one time, they used to share a building with Soldier of Fortune magazine. Why I know that? I have no idea.
In Richmond there is a huge cigarette factory just off 95. They have tours that somewhat surreal. Visitors are put in a train of golf carts, each guest with a headset to listen to the young lady tour guide. The train of cars travels through a plexiglas tunnel that goes down a hallway with people walking to and from the lunchroom or whatnot. Very strange. Seem they have had some trouble with protesters.
They have five assembly lines. When all of them go full-blast for 24 hours, they can produce a billion cigarettes.
At the end they give you a token, like a poker chip you can use at the gift shop to get a pack of smokes.
The brewery tour is fun, but you only need to do it once. A word of warning about the Clydesdales, though. You know those signs on the stalls saying something like “Do not pet me. I bite”? Those aren’t just for decoration.
Another good brewery tour is the Red Hook brewery in Portsmouth, NH. It costs a dollar, they give you a glass to take home, let you taste all kinds of beer, and then give you a few postage paid postcards that you can use to send drunken ramblings to your friends before you leave. They even mail them for you.
The place that made pink flamingoes in Lowell, MA was really cool, but they closed earlier this year, I believe. Another neat one was the Ball Glass factory in Cartaret. My dad was an HR guy there, and I got to see all the really cool stuff. My brother still has a glass chunk he picked up off the floor where it fell.
Here’s a Chicago area list. I would have suggested the Jay’s potato chip tour which is required for every elementary school’s field trip roster but it’s closed. 
Definitely go for that! I’ve been through the Caterpillar plant in Clayton, NC. I was with an ASME tour group, so we were able to actually walk around on the production floor. We also got to eat dinner in their cafeteria (like a small convenience store with a buffet!).
I’ve toured the former Cates Pickle Company in Faison, NC on numerous occasions. They were bought out by Dean Foods, which in turn was bought out by Suiza (sp?); the factory is mostly still there, but it’s a shadow of its former self.
I’ve also been through Mt. Olive Pickle Company, including their distribution center and the building housing their newest production line. They generally don’t give tours to the public, but they will have a spot on an upcoming episode of “Unwrapped” on the Food Network if you’re interested.
As part of job interviews, I’ve had a chance to tour Eaton (this division made various hoses, like what’s used on the Jaws of Life) and Altec (trucks with lift buckets, like your power company uses).
Ben & Jerry’s tour is awesome! Cabot (also in Vermont) had a pretty nice place too. I also toured a Budweiser facility in New Hampshire many years ago…very nice place (especially the horses – I got a little plush Clydesdale at the gift shop).
I went on a tour of a cigarette plant in North Carolina as a child. I don’t remember where it was, though I do remember the big plexiglass windows overlooking the production floor.
The factory tour capital of the world. Really!
I grew up in York and visited most of the ones listed. You really only need to see one snack food factory, though it is interesting. Family Heirloom Weavers (a textile) is one of the more interesting on the list. I enjoyed a tour of the local paper mill, but I don’t think they do those regularly. The local incinerator was surprisingly interesting. The tour of Three Mile Island was extremely boring.
My favorite part of that is- a good many of them aren’t even in York County!
Huh, that’s weird. Of all the places I went, only Harley is listed on that site. And all of the tours I went on were located in York County.
BTW, it probably won’t help anyone who isn’t in PA already but our local station PCN has a program on daily calld PCN Tours which goes through out the state and give tours of a number of different factories and businesses. It’s like a local version of Discovery’s How It’s Made.
I went on an interesting “factory” tour about four years ago - Dannemora prison decided to have a day of public tours. My brother and I decided to go (despite the fact that we both work in prisons and had in fact worked in Dannemora itself years before). It turned out to be insanely popular - they got about ten times as many people as they expected and you had to wait in line for three hours to take your thirty minute tour.
About 12 years ago, I lived in a suburb of Kansas City. They built a new Juvenile Detention Hall just down the street from my apartment. The weekend before they opened for business, they gave tours. It was really interesting, but also kind of weird. The tour guide was like a tour guide you might see anywhere – a youngish woman with a nametag, cheerfully explaining things and taking questions. Kind of a disconnect as she smiled and said things like, “And here’s the cell. Note the polished steel mirror. Of course, we don’t have any glass in the cells…”
I work in industry and get non-public tours. Here are some impressive things to see if you can get a public look at:
Arc furnaces. These things sizzle and boom and rumble and snap and smoke like hell. Many people can’t be dragged within 50 feet of one, they’re so attention-getting.
Cleanrooms where they manufacture integrated circuits, especially the “front end”, which is the part where they are creating active circuit components on the silicon, as opposed to the first metal (where they start connecting things with broken layers of metal plating) and the back end that follows. Contamination and vibration control are amazing. It’s not unusual to see a 500 hp or more fan driving the HVAC system and the ceiling to be 95% filters. Floors are always perforated metal panels so the dirty air falls out right away. I saw one 25 years ago in Essex Junction, VT where they had a 100 foot square cleanroom (though this one was primarily for making hard disk drives), suspended on sprung cantelevers to reduce vibration. The lunchroom in that facility could seat 7000 people and was the largest restaurant in the state.
Power plants of almost any sort are fascinating. The plant on Nantucket Island, at least 30 years ago, was entirely large diesel engines, and you could stroll around them and touch them as they thundered along.
If you are ever in Seattle, check out Theo Chocolates. You have to make reservations and it costs a few bucks, but it’s interesting and there are lots of samples.
Best part is buying dented boxes of tea for a buck after the tour! The tour is best if they are in production, so visitors should go in the fall & winter. They don’t make as much tea in the summer.
I came in to suggest the Jack Daniel’s tour. It was fascinating.
The Freia chocolate factory in Oslo. Okay, the tour is just a normal factory tour (except for some happy Munch paintings in the employee cafeteria), but man oh man, are they generous with the free samples 