Most recent find, one morning last month, was a driver's license and a lot of business cards, all from different businesses; on the backs of which the owner (well, the loser, technically) of the license had written all his bank account numbers, email addresses, user names, passwords, etc. Including his cell phone number, labeled "my cell phone number." I called it. He answered. I mailed it all back to him. On the way home I found a bunch more of his stuff, including old B&W photos of family members. I sent him another envelope.
A week later I got a check for $50 in the mail, with "thanks" written on it. "You're welcome!" I thought, as I deposited it.