They say a watched pot never boils, but a covered one boils extra quickly, saving cooking time--and energy. Using smaller appliances, like a microwave, toaster oven, rice cooker, or crock pot when appropriate to the task; choosing the right size pan and burner for meals prepared on the stove; and keeping the oven door closed while baking are other great ways to conserve energy in the kitchen. It also doesn't take as much energy to reheat food as it does to cook it in the first place, so make enough for leftovers!
When buying new appliances, look for the Energy Star label. And when picking out new pots and pans, skip the nonstick ones. Teflon is made with a chemical, perfluorooctanoic acid (PFOA), that is a "likely carcinogen" (according to the EPA) and a major polluter of air and water near where it's produced. Old-fashioned cast-iron pots and pans are a safe alternative, as are those made out of anodized aluminum and stainless steel (unless you're allergic to nickel).