I've accumulated quite a nice little store of Oak, Walnut, maple and other species when driving past the place a local cabinet shop piles its discards to await the 'trash collection' folks and or dumpster divers.
I collected lots of scrap marble countertop from a place along 321 that put all it's scraps in a similar pile for a similar reason - they shared the location with me when I called them to ask "Got any marble/stone countertop scraps I could have?"
I happened upon another stone countertop place (coincidently in Granite Falls, NC) once a few years back and saw all these pieces of plastic that had been used to make templates for the countertops of the rich and not so famous and asked "Can I take some of that stuff?" When I got it home I took my razor knife and hot glue gun and laid out the patterns for my two kitchen countertops, then used those templates to build the real things.
So my advice for Corian (or equivalent) hunters is to ask Lowes or Home Depot for the name of the company that makes Corian (or equivalent) countertops for them. Or, just Googol "Custom Corian Countertop YourCity, Your zip" and make a few phone calls.
Or, should you drive by a place that has large slabs of granite looking stuff displayed, pop in and ask them "Do you make countertops out of Corian? 'cause I could use a piece of sink cutout (32+/- x 22+/- as a rule)"
I also know how to recycle zip ties and sell used lottery tickets @ half price to folks who'd rather lose the lottery for less.