I found $83 in cash near my apartment building. I posted a sign in the communal area that said I had found some cash, and that anyone who was able to tell me how many dollars I found can have it. I got three calls and they were all just guessing. One guy said, "uhhh, was it $100?" So I kept the money and never felt too bad about it.
I have also found a few beanies and a scarf that I picked up, and used, while riding.