Postcards
I bought 20 second hand postcards at a flea market in New York. I took them back to London and re-packaged them, adding a return address label with my details.

I then re-sent the postcard to the addresses they had originally been sent to. Most of them were places on the East coast of America. I was interested to see wether any of the postcards would reach the same person they had the first time.

I am still waiting for any response although three of the postcards were returned by the US Postal Service due to the addresses no longer existing.