I run and when I see money on the road or sidewalk I ALWAYS pick it up - doesn't matter if it's a twenty or a penny. All of my found money goes into a special jar to be spent at the end of the year on new running shoes. This year has been exceptionally lucrative and I am probably up to about $90 so far (a $20 and a few $5s really help the total).
I find a lot of bungee cords on the road but never bother picking them up. People forgetting that there are bungee cords in the beds of their trucks and losing them must be what drives 80% of the bungee cord purchases in this country.