I can't imagine anyone converting from one religion to another on the basis of something they found on the ground. The idea of picking up a profoundly life changing piece of refuse just plain eludes me. That being said, here in Kentucky there are diverse religious groups who bank on just that.
The Scientologists for one leaflet the U of L campus regularly and also take out ads in all the local "alternative newspapers". One of my fondest hopes in school was to slip on a pile of Scientology personality tests in front of Ekstrom Library, blow out a knee, and live the rest of my life on L. Ron's coin thanks to a fat lawsuit. Sadly that never materialized, but those silly "Oxford Personality Measurement" things litter the college grounds like cherry blossoms with the coming of each new semester.
Likewise the Seventh Day Adventists, whose hilariously titled book "National Sunday Law: Forces Unite Against Stupendous Crisis" shows up regularly just about anywhere you can fit a pile of the things. I first encountered them when I worked at a Subway during college - every week or so, a man who looked like George Lucas would trundle into the store, leave a dozen of the things on the tray return shelf above the garbage can, and then slink mysteriously back into the night. The Seventh Day Adventists, if you're unaware, make it a centerpiece of their faith that the sabbath should be Saturday rather than Sunday. Christians who use Sunday for the sabbath have therefore obviously been corrupted by a demonic conspiracy and are going to go to special hell. While I'm an atheist, I tend to split the difference by not doing in work on Saturday or Sunday and it seems to have worked out okay so far.
Finally, of course, we come to probably the most ubiquitous form of garbage can proselytizing- Jack Chick tracts. These fearsome little numbers are available in bulk Chick.com and spout a fiery anti-Catholic, anti-gay, anti-science, anti-everything-but-Chick-Tracts form of fundagelical Christianity. They've also become a token of American pop culture, showing up as music videos and even being modified to preach the virtues of prostrating yourself before Cthulhu.
In any event, I stumbled across one of these today in, of all places, the john at a Panera Bread Co. It wasn't even an appropriate one about not being a yuppie or something, it was "No Fear?", which is just about some guy who kills himself and goes to hell. Most Chick Tracts end with someone in hell, often after getting smote down by a 3o-ft tall faceless Yahweh.
I was disappointed not to get one of the good ones like "Dark Dungeons", but "No Fear?" is still going right to the top of collection of mass-market proselytizing paraphernalia. (The previous prize of my collection was a creationist leaflet called "The Big Bang is like a Terrorist Bomb".) If you want, for whatever weird reason, to look at all of Chick's work, they're all available on his website for perusal, some them in multiple languages or "adapted for black audiences", whatever that means. If you were only going to read one, I'd recommend this howler in which Chick explains how dinosaurs went extinct. (In a nutshell, they were hunted to extinction after the Flood because the destruction of plant life made the air too thin for them run away quickly.)