A few years ago I considered trying to sell poison ivy. I was looking for something I can get for free but that someone somewhere is willing to pay for. Ultimately there were too many obstacles for me, but I'm convinced the idea is sound.
Last year my daughter went to an outdoorsy day-camp. One of their projects was to gather up plants to make headdresses. She gathered up an armload of poison ivy and draped it over her head and arms. The camp counselors quickly cleared it off and gave her a good scrubbing, but to no avail. 24 hours later a rash developed, and at 36 hours she was a MESS. But she was a total trooper about it, only crying once when the itchiness got out of control on the way back from the doctor. We found that a lukewarm bath full of baking soda made her feel a lot better, even if it really just took away the feeling of helplessness.