So...I have never found anything of note on a trail, though on trail I have lost a nice flashlight and a bandana that had great sentimental value. As for the roads, I have never found any money (I guess because it's unusual for $$ to fly out of a moving vehicle). But what I do find with some regularity, in descending order, are:
--Bungee cords: the # 1 find--probably fall off farm wagons or pickup trucks
--Alcohol: unopened cans and bottles of beer (never any hard liquor)
--Pron (misspelled intentionally for firewall and search purposes): magazines, once a DVD
--Hardware: nuts, bolts, washers, nails
--Tools: a hammer and once a big combination wrench (a 2" beast)
(Photo credit here)
I assume the pron and alcohol are items tossed by teenagers rather than risk taking them home where they could be discovered.
As for the big combination wrench, I hauled it about a mile till I got to Fort Frederick State Park (in MD) then gave it to a maintenance worker. Too heavy to lug for the remaining 3 hours back to the car.