The answers are: no, no, and sort of.
The Ocean Spray bottling plant and warehouse are still there, but tours haven't been given since spring 2000. (This was a cool tour where you could watch the little red buggers being sorted, crushed, and blended into a variety of cranberry products; at the end of the tour was a gift shop and free juice bar).
The original Kidd Marshmallow plant blew up in the Pepcon incident in May 1998 (a massive explosion at the rocket-fuel factory next door to Kidd; two people were killed). The marshmallow plant was rebuilt (it's now called Famous Brands International), but the tours were discontinued.
(You didn't ask, but somebody else did, and we can confirm that the Vegas Chips potato chip factory, which offered tours, is also no more.)
Ron Lee's World of Clowns is still going strong, but it's now different than it was when you probably visited. They still have the showroom, full of ceramic clown figurines, including Lee's signature character Hobo Joe, as well as characters from Looney Tunes and Disney, Emmitt Kelly, even Vegas icons like Lance Burton. However, the Carousel Café is gone and the tours are now restricted (no one under 18 is allowed and rather than self-guided, you're given a personal tour; we're told it's mostly for clown collectors).
Ron Lee has also moved from its original location. It's now at 7685 Commercial Way, Suite A, Henderson -- ironically in terms of this answer, right in front of the Ocean Spray building. It's off Warm Springs Rd. about a quarter-mile from the old location; call 702/434-1700 for directions.
You can click on Activities on the home page of this Web site (under the Vegas Info banner), then go to Exhibits and Free Spectacles for complete and up-to-date lists of similar attractions around the valley, such as tours of a chocolate factory, dairy, and cigar operation.
