Buy more locally produced food. You can reduce emissions from transportation by buying from farmers markets and eating foods in season rather than foods shipped in from around the globe.
Use alternative transportation to work, school, or your place of worship. This is a good way to slow down and find a few extra minutes for contemplation during Lent.
Eat less meat. Reducing the amount of meat you consume, even just one day a week, will make a difference in your carbon footprint.
Turn down your thermostat. Grab a blanket and add an extra layer of clothing. Even one degree lower will add up to big energy savings.
Try a media fast. It can be very rewarding to turn off televisions, computers, and radios a few nights a week and sit down to a board game with your family.
More ideas here.