helpsaveearth.org not only lists actions which you can take to help save the environment, but also rates each action according to how easy it is and how much impact it has.
SourceMap is an open source, open data tool that allows people to make and share maps depicting the environmental impacts of products, food, and travel. I've linked to one example---the carbon impact of a can of Coca-Cola---but you can explore the site to find more, or create your own maps.