Here's a neat tool from American Public Radio - an educational game that calculates your global ecological footprint.
Overconsumption is at the core of virtually all environmental problems, and most of that consumption is stuff that we don't even think about. Especially in the fast-paced world of the US middle class, we do things the way we always have. There isn't time to think about each action individually, and options are limited (e.g. transportation of goods has a big impact, but for many products there is simply no option to buy local). But education and incremental changes will help.
So play the game, get some ideas, and think about how to improve your lifestyle. And for inspiration, check out Malkolm Boothroyd's Bird Year.