Well, I did a flyer campaign in my neighborhood in my undergraduate days. I was sick and tired of folks parking their cars on sidewalks, blocking pedestrians and cyclists. So, I printed up about 50 copies of flyers and paced them on several cars on several streets in my parents' neighborhood that read:

"Move Your Car, Please. It's Called SideWALK for a reason!"

Of course, I didn't get to see their reactions in the morning because I did it really, really late at night, and I had late classes the next day, so I did not get up early enough to see the looks on their faces.

It probably wasn't ethical to place something on someone's private property, now that I'm looking back on it, but that kind of thing is endemic in Miami: folks paking their cars and gas-guzzlers on sidewalks and bike/job paths. I'm so sick of it.