I have found a bunch of stuff, but I never pick anything up. My commute is few miles on country roads and few miles on city roads. the most stuff I find on the country roads, lots of bungee cords, some wrenches, and screw drivers, and even a machete in its casing which I didn't pick up because I don't want to ride into the city carrying a machete in my bikes. I often ride by lots of cop cars. Beside I was afraid that machete had been use for something bad and just throwed out there, I just didn't want to find out.
I do keep my eyes open for $100 bills, I would pick these up in a heart beat. Other stuff I am not too excited about it.