Here are two ways I'm contributing to Peace in the World:
1. If I see a penny on the ground, I leave it there for someone else to pick up. I figure I'll get more good luck that way. (Note: as the size of the money on the ground goes up, my willingness to do this diminishes. Not sure what that says about my level of Enlightenment.)
2. When I find a flash drive in a classroom, I look at the files to see who it belongs to, then email the person. It takes a few minutes, but I get fabulous little thank-you emails back. Which makes me feel good.