Look Up Pollution Levels in Your Area
This We Know is a new site with a grand goal: to synthesize all public government data into a single semantic web application. They've got a way to go, but the site does currently let you look up which areas have the highest unemployment, for example, or the most nomadic population. But the most compelling stuff on the site is probably the information about pollutants. You can type in your zip code and get a list of factories in your area and all the dangerous junk they emit, by weight.
I tried it. Within 24 miles of my house are 350 factories emitting 4,303,560 pounds of 104 different pollutants.
There's a 3M factory in my neighborhood that emits methanol, dichlorodifluoromethane, and nitroglycerin. Other factories in the area emit lead, ammonia, and an array of additional unpronounceable pollutants. I don't know what all these chemicals are, or which are most dangerous, but it's important that this information is accessible.