When cooking a casserole or a yummy chocolate souffle, use ceramic or glass baking dishes; these materials outperform metal and will allow you to lower the temperature of the oven by 25 degrees Fahrenheit. Lower heat means less energy.
Cash from trash! If you have scrap metal lying around the house -- wiring from an unfinished project, a brass bed, leftover construction material -- don't toss it, recycle it! Look up "scrap metal dealers" in your phone book and drop off your recyclables. They'll pay you cash for your trash, and it'll all get recycled into new metal products. Use the cash to treat yourself to something nice.