We put most of our leftovers in the wash stall, DH has a piece in front of his work bench and when a new horse started pawing the concrete in front of his stall we put a piece there, like a door mat. Stopped his pawing immediately and now he uses it as a place mat for his alfalfa!
We had the same leftover pieces. I use them as stall doormats in the aisle, like someone else mentioned.
I also made them into poor man's no-cast strips. We had a horse who occasionally would get cast in a stall, so I screwed the strips into the stall wall horizontally 2 or 3 feet up from the ground. They looked like a black racing stripe. Unsure if they solved the problem or if he sorted out in his head how NOT to lay down so close, but I never had to get him uncast again.
"And now," cried Max, "let the wild rumpus start!"
Even small pieces can be very useful INSIDE the house! Put them under the feet of your washer and dryer to cushion some of the vibration and diminish some of the noise, especially if your laundry room is upstairs in a very old wooden farmhouse.
Other small pieces - hand-sized - can serve a very similar purpose under the feet of a treadmill. Mine has been much quieter since I did this... although I must admit that even after many soapy scrubbings of those pieces of old rubber mat, the treadmill does have a faint odour reminiscent of, well, a stall.
Target shooting. DH and his dad took an old pallet and screwed the leftover strips of stall mat to it. Easy to staple the paper targets onto, and the rubber slows down or stops the bullets, depending on what they're shooting.
we cut them down and put them on top rail of our wooden dutch doors. Stopped horses from chewing on doors and looks nice too.!!
Works Great. Plus you can replace them if they get messed up, and cheaper than fixing doors.