I worked at a concert venue in Boulder, CO for a year when I was younger. One of the great benefits of the job was getting to pick up everything that was dropped on the floor during shows. The lights went back on during the load-out, and it was almost garunteed that there was enough for everyone. I'd come away with money, pills of all sorts (pharmaceutical and illicit), pot, and blow on the regular. That was back before I had used needles myself, and it wasn't unknown to find a rig on the ground... which wasn't so cool.
When I was even younger, I had been at a three day music festival in northern Florida. The type with jambands and James Brown... and copious amounts of drugs. On the first night we had not gotten any sleep, and were wandering around in a large field that didn't have campers, but had been used as a pathway to camping and for a massive, noisy drum circle. As we crossed the field, which had to be 300m x 300m, we all kept on the lookout for ground scores. We came away with more than 5 grams of MDA (found divvied up into "packs" meant for several dealers), 1/2oz of pot, several 1/8th's of mushrooms. That was a good weekend.
I've been known to find a gram of bud here and there... under the couch or in a drawer, or a random benzo that I had placed somewhere and discovered much later.