For most people, posting picture online is just for fun. But posting picture online can also be a productive way to discover new things.
A viewer recently tipped me off to the site reckonthatis.com. It was created by an Alabamian, so it's no surprise its name comes from the old southern vernacular "what do reckon that its?" The site's intent is just what you might imagine. People post pictures of things they can't identify, and ask other people for the answers. The site is good for entertainment, too- as some of the answers can be pretty funny.
A site called ifoundyourcamera.net is a place where honest folks who have found lost cameras can post photos that are in the camera's memory. The idea is that the person who lost the camera will see their shots online, and get in touch. Some users are going beyond its intent. One person cam away from an auction with some old black and white pictures, and is now working to learn more about the people in them.