Here's a very helpful link with a complete industry list from 1957:
http://readingmodeler.com/modules.php?n ... rt&sid=178
As you can see there were about a dozen customers, but most of them used the team track. Apparently the old team track was around where the parking lot for the park is today. At some point it was moved to the siding that eventually went on to the feed mill. That siding still exists today up to the Route 100 crossing and is sometimes used to store MOW equipment.
Tyler Pipe (East Penn Foundry before 1964) had their own spur going into the east end of the complex from the old passing siding off the westbound track. From looking at old aerial photos, they got cars into at least the 70s. The Tyler Pipe siding appears in my 1990 Conrail ZTS map, but not in the 1993 one, so the spur was probably removed sometime around then. However, they could have stopped receiving cars long before that date. The Dries "siding" (which appears to have just been a track spot on the aforementioned passing siding) was removed at around the same time.
Singmaster Lumber (apparently Shelly's Lumber now) had a siding into their facility along aptly-named Lumber Street. I don't know when they stopped getting cars, but you can still see part of the siding today, albeit covered in tree growth. Considering a small warehouse was built on top of this spur in the early-to-mid 90s, I'm sure it was unused for quite some time before that. The feed mill (which would have been D.D. Fritch, and later Agrico) was probably the last customer in Macungie proper. I believe they did get covered hoppers of feed grain and/or fertilizer into the 90s. I'm not entirely sure where the Texaco siding would have been, but I think it was near the current location of the Buckeye Pipe spur. Speaking of which, although Buckeye does show as a team track customer in the shipper's guide, they didn't get a large-scale amount of cars until the siding was constructed just east of town around 2006.
As a side note, according to this link
, in the 1800s Macungie also had a tannery and, for a brief time, an iron furnace. I'm sure they both would have received railcars when they were in operation.