Walking home from the gym, I looked down and found a set of keys on the ground. Yikes, I felt bad for whoever lost them. That would be no fun. I didn't know if I should leave them there, and hope the person would backtrack and find them, or what.
Then I thought of craigslist--I could post an ad and hope they'd think of craigslist too. So, I took the keys, and got on Craigslist. The person had already posted an ad for his lost keys that matched exactly what I had found--even had a photo. Now he's got his keys back. Thanks Craigslist, that was easy, and good karma too!