At work in the secure area when locking up I found a 10 inside the door. I didn't know what to do with it so I tacked it on the bulletin board by the door. Really obvious. Nobody took it for 2 weeks (which is kind of remarkable), so I took it back to buy lunch.
I found a twenty in the snow on the street in cambridge. But it was new snow and easy to follow the tracks. It led to the security guard at the University. He was really thankfully to have it back.
Later that spring I found a crumpled $50 blowing down the street. It was near the faculty club. "Tumble Money" my partner said. Also 50s aren't really common. I kept 30 and donated 20 to charity.
But lamentably my good fortune in the finding of cash has come to an end. Perhaps the rise of the credit card changed my fortunes.