I haven't picked up any since spring but Lowe's in Carlisle had stacks of them in the back parking lot at the time. The front of the store faces PA 641 and the rear is on PA 74. They were stacked near the curb and were free for the taking. But like I said, I haven't been there since April so I don't know if they are still putting them out.
Just make a drive around back of some strip malls. We have a couple guys that I see daily behind my place and always is getting pallets from some of the Big Box Stores down the way from me. I personally go to a tile store I deal with, I got my buddy saving me the "pretty" ones for my furniture projects.
I have a couple dozen plain pallets in pine. If the Agway guy fails to take them with next delivery you can have them. I get a few each month from deliveries.
Man, I see pallets behind tons of store around here...Walmart, Lowes, HD, Menards, TSC, Rural king, NAPA, sometimes Auto Zone, Fastenal, even Kohls on occasion. Tons of others too. Are you looking to stack wood on 'em or burn 'em?
Stack wood. I've asked around a whole lot of places like you mentioned. Most of them "recycle" their pallets now. Occasionally, I'll get a hit, but lass than 1 in ten inquiries.
You need a small stack of business cards and a magnetic vehicle sign that states, "Pallet Recycling".... Done.