I was outside working on my artcar, and peeling off old disks, and wanted to dispose of them. Usually, I throw them in my garbage can, but I was parked a bit down the street, and was in front of someone else's house and garbage can. there were also a number of cardboard boxes and other assorted "we just moved out in a hurry" detritus next to the can. so, instead of throwing stuff in the garbage can, which was already pretty full, I decided to just toss my garbage in the boxes. As I leaned over to tuck a couple of diskettes into the side of a box, I saw something curious that did not seem to belong in the garbage, resting as it was on top of a bunch of longneck beer bottles.
I picked the item up and brought it inside, where my soon-to-be-ex housemate was talking with friends/business partners. I addressed M, who's in his 40s, and said "Is this what I think it is?" He opened the Ziplock and smelled it, and confirmed my suspicion: someone had thrown away about 3-4 tablespoons of marijuana.
Since I don't smoke marijuana, I left it for them, which seemed to assuage a lot of the tensions between me and my soon to be ex-housemate.
the other ironic postscript: I told a neighbor I'd found something odd in the trash, and she said "was that pot? i saw that, and figured it couln't be, because who would throw that away?". she pointed out to me that while the contractors were tearing up the planks of said neighbors porch, there was an odd item, covered in spiders and dust, that was possible pulled from underneath the porch as they were renovating it. It was a 2 foot tall bong, featuring a relief sculpture of "Chef" from South Park" on the base. It's now a garden ornament in my back yard.