Usually don't find much in the city because we have street cleaning. Sometimes I find micro USB cables that are always run over (shame because I could use more of those!) I also find working Bic lighters with fuel still in them pretty often. I haven't bought a lighter in years. One time on my commute to work, I found a box full of bike parts on the curb that someone put out. I took some hose clamps and a bottle of Tri Flow and left the rest.

A few years back, when I did a 2500 mile tour of the Northeast / Atlantic Canada:

• While climbing a mountain in West Virginia, I found a whole box of home canned goods in mason jars on the side of the road. I took one that looked like cabbage, and another that looked like some kind of jam. I opened them at my friend's place when I got to DC. We pitched the cabbage because it smelled a little funky, but we made French toast with the jam and it was delicious!
• Found 5 license plates on the side of the road. Pennsylvania, Quebec, Nova Scotia, and 2 Newfoundland and Labradors.
• Lots of bungie cords. I took a few for strapping things to my rack.