Believe it or not, reducing food waste is one of the easiest ways to go green and save money doing it. The U.S. Department of Agriculture estimates that about 30 cents of every dollar we spend on food we end up throwing away because what we've bought spoils, or expires, or because we've just bought too much. The solution? Put leftovers in the front of the fridge, not the back where you might forget about them. Try to plan menus in advance, then grocery shop with an ingredients list so you buy what you really will use. Go to the grocery store just once a week - after "leftovers" night, if possible, and when the fridge is almost empty (which means you've eaten what you've bought). If you need to make an emergency milk run, do it at the local convenience store, where you won't be tempted to buy more than you need at the time.
Added benefit: the money you save wasting less frees up your budget to buy some delicious organic chocolate!