There's an ongoing cleanup of Baugh's Cave in upstate NY, led by Joe Armstrong. He's hauled out tons and tons of material from this cave in the past few months, which has been a local dump site for the past thirty years. In the spring, this cave wasn't even the 30-foot pit is is now, but a 10-foot mound of garbage.
Stuff found so far:
Bathtub
Washing machine
Backseat of a car
Water heater (which might actually be a furnace: it's at the bottom of a heap of dirt/trash which is being worked through)
Exercise Bike
Artificial fiber rugs (natural fiber rugs have helpfully rotted away)
Microwave
My Little Pony
Multiple radios
Unshattered plates
Shattered plates
Giant chunks of some sort of concrete
Enough tires to build your own playground
Enough bricks to build a deck
Enough lumber to burn every Baugh's litterer in effigy
What other weird stuff have people found in cave cleanups?