I made a few changes several years ago to reduce my carbon footprint, and found that we saved money in the process. I wish I had done it sooner.
Cloth napkins: to save trees, I use cloth instead of paper.
Parchment paper: I use parchment paper instead of aluminum foil to line pans in the oven.
Old clothes: I cut old T-shirts for rags, and keep the sleeves to use as disposable ones.
Grocery bags: I line the trash cans around the house with produce and grocery bags.
Insulating pipes: we insulated our hot water pipes which allowed us to lower the temperature on the water heater.
Recycling cans: we take them to a local metal recycle company and get cash.
Toss a dry bath towel in the dryer: it reduces the time it takes to dry the laundry.